One Third of Americans Already Had COVID-19 During 2020

Undocumented infections accounted for estimated three-quarters of infections last year

From: Columbia University Public Health Now

August 26, 2021 – A new study published in the journal Nature estimates that 103 million Americans, or 31 percent of the U.S. population, had been infected with SARS-CoV-2 by the end of 2020. Columbia University Mailman School of Public Health researchers modeled the spread of the coronavirus, finding that fewer than one-quarter of infections (22%) were accounted for in cases confirmed through public health reports based on testing.

The study is the first to comprehensively quantify the overall burden and characteristics of COVID-19 in the U.S. during 2020. The researchers simulated the transmission of SARS-CoV-2 within and between all 3,142 U.S. counties using population, mobility, and confirmed case data.

Infections were more widespread in some areas of the country. In areas of the upper Midwest and Mississippi valley, including the Dakotas, Minnesota, Wisconsin, and Iowa, more than 60 percent of the population is estimated to have been infected by the end of 2020. In five metropolitan areas the researchers examined, 48 percent of residents of Chicago, 52 percent of Los Angeles, 42 percent of Miami, 44 percent of New York City, and 27 percent of people in Phoenix, had been infected in the same timeframe.

Testing picked up on a growing number of infections but offered an incomplete picture. The portion of confirmed cases reflected in the study’s estimates, i.e. the ascertainment rate, rose from 11 percent in March to 25 percent in December, reflecting improved testing capacity, a relaxation of initial restrictions on test usage, and increasing recognition, concern, and care-seeking among the public. However, the ascertainment rate remained well below 100 percent, as individuals with mild or asymptomatic infections, who could still spread the virus, were less likely to be tested.

“The vast majority of infectious were not accounted for by the number of confirmed cases,” says Jeffrey Shaman, PhD, professor of environmental health sciences at Columbia University Mailman School of Public Health. “It is these undocumented cases, which are often mild or asymptomatic infectious, that allow the virus to spread quickly through the broader population.”

One in 130 Americans was contagious at year’s end. Roughly 1 in 130 Americans (0.77%) was contagious with SARS-CoV-2 on December 31, 2020. A similar percentage (0.83%) was estimated to be latently infected, i.e. infected but not yet contagious. In some metropolitan areas, the percentage of individuals who was contagious at year’s end was much higher.

Fatality rates fell with strengthening treatments and public health measures. The percentage of people with infections who died from COVID-19 fell from 0.8 percent during the spring wave to 0.3 percent by year’s end. Urban areas like New York City that peaked in the spring saw the worst numbers for reasons that include delays in testing availability and masking mandates, overwhelmed hospitals, and lack of effective treatments.

Cities peaked at different times of the year. New York and Chicago experienced strong spring and fall/winter waves but little activity during summer; Los Angeles and Phoenix underwent summer and fall/winter waves; and Miami experienced all three waves. Los Angeles County, the largest county in the U.S. with a population of more than 10 million people, was particularly hard-hit during the fall and winter and had a community infection rate of 2.4 percent on December 31.

A new pandemic landscape for 2021. Looking ahead, the authors write that several factors will alter population susceptibility to infection. The virus will continue to spread to those who haven’t yet been infected. While vaccines protect against severe and fatal disease, breakthrough infections, including those that are mild or asymptomatic, will contribute to the spread of the virus. The current study does account for the possibility of reinfection, although there is evidence of waning antibodies and reinfection. New more contagious variants make reinfection and breakthrough infections more likely.

“While the landscape has changed with the availability of vaccines and the spread of new variants, it is important to recognize just how dangerous the pandemic was in its first year,” concludes Sen Pei, PhD, assistant professor of environmental health sciences at Columbia University Mailman School of Public Health.  

Additional authors include Teresa K. Yamana, Sasikiran Kandula, and Marta Galanti at Columbia Mailman School.

https://www.publichealth.columbia.edu/public-health-now/news/one-three-americans-already-had-covid-19-end-2020

Research Finally Reveals Ancient Universal Equation for the Shape of an Egg

From:  The University of Kent

August 27, 2021 – Researchers from the University of Kent, the Research Institute for Environment Treatment and Vita-Market Ltd have discovered the universal mathematical formula that can describe any bird’s egg existing in nature, a feat which has been unsuccessful until now.

Egg-shape has long attracted the attention of mathematicians, engineers, and biologists from an analytical point of view. The shape has been highly regarded for its evolution as large enough to incubate an embryo, small enough to exit the body in the most efficient way, not roll away once laid, is structurally sound enough to bear weight and be the beginning of life for 10,500 species that have survived since the dinosaurs. The egg has been called the “perfect shape”.

Analysis of all egg shapes used four geometric figures: sphere, ellipsoid, ovoid, and pyriform (conical), with a mathematical formula for the pyriform yet to be derived.

To rectify this, researchers introduced an additional function into the ovoid formula, developing a mathematical model to fit a completely novel geometric shape characterized as the last stage in the evolution of the sphere-ellipsoid, which it is applicable to any egg geometry.

This new universal mathematical formula for egg shape is based on four parameters: egg length, maximum breadth, shift of the vertical axis, and the diameter at one quarter of the egg length.

This long sought-for universal formula is a significant step in understanding not only the egg shape itself, but also how and why it evolved, thus making widespread biological and technological applications possible.

Mathematical descriptions of all basic egg shapes have already found applications in food research, mechanical engineering, agriculture, biosciences, architecture and aeronautics. As an example, this formula can be applied to engineering construction of thin walled vessels of an egg shape, which should be stronger than typical spherical ones.

This new formula is an important breakthrough with multiple applications including:

1. Competent scientific description of a biological object.
   Now that an egg can be described via mathematical formula, work in fields of biological systematics, optimization of technological parameters, egg incubation and selection of poultry will be greatly simplified.
2. Accurate and simple determination of the physical characteristics of a biological object.
   The external properties of an egg are vital for researchers and engineers who develop technologies for incubating, processing, storing and sorting eggs. There is a need for a simple identification process using egg volume, surface area, radius of curvature and other indicators for describing the contours of the egg, which this formula provides.
3. Future biology-inspired engineering.
   The egg is a natural biological system studied to design engineering systems and state-of-the-art technologies. The egg-shaped geometric figure is adopted in architecture, such as London City Hall’s roof and the Gherkin, and construction as it can withstand maximum loads with a minimum consumption of materials, to which this formula can now be easily applied.

Darren Griffin, Professor of Genetics in the University of Kent and PI on the research, said: ‘Biological evolutionary processes such as egg formation must be investigated for mathematical description as a basis for research in evolutionary biology, as demonstrated with this formula. This universal formula can be applied across fundamental disciplines, especially the food and poultry industry, and will serve as an impetus for further investigations inspired by the egg as a research object.’

Dr Michael Romanov, Visiting Researcher at the University of Kent, said: ‘This mathematical equation underlines our understanding and appreciation of a certain philosophical harmony between mathematics and biology, and from those two a way towards further comprehension of our universe, understood neatly in the shape of an egg.’

Dr Valeriy Narushin, former visiting researcher at the University of Kent, said: ‘We look forward to seeing the application of this formula across industries, from art to technology, architecture to agriculture. This breakthrough reveals why such collaborative research from separate disciplines is essential.’

               https://www.eurekalert.org/news-releases/926715 

Basics of "Quantitative Easing"

Quantitative easing (QE) is a monetary policy whereby a central bank purchases predetermined amounts of government bonds or other financial assets in order to inject money into the economy to expand economic activity.  Quantitative easing is considered to be an unconventional form of monetary policy, which is usually used when inflation is very low or negative, and when standard monetary policy instruments have become ineffective.

Similar to conventional open-market operations used to implement monetary policy, a central bank implements quantitative easing by buying financial assets from commercial banks and other financial institutions, thus raising the prices of those financial assets and lowering their yield, while simultaneously increasing the money supply.  However, in contrast to normal policy, quantitative easing involves the purchase of riskier assets (rather than short-term government bonds) of predetermined amounts at a large scale, over a pre-committed period of time.

Central banks usually resort to quantitative easing when their nominal interest rate target approaches or reaches zero. Very low interest rates induces a liquidity trap, a situation where people prefer to hold cash or very liquid assets, given the low returns on other financial assets. This makes it difficult for interest rates to go below zero; monetary authorities may then use quantitative easing to further stimulate the economy rather than trying to lower the interest rate further.

Quantitative easing can help bring the economy out of recession and help ensure that inflation does not fall below the central bank's inflation target.  However QE programmes are also criticized for their side-effects and risks, which include the policy being more effective than intended in acting against deflation (leading to higher inflation in the longer term), or not being effective enough if banks remain reluctant to lend and potential borrowers are unwilling to borrow. Quantitative easing was undertaken by all major central banks worldwide following the global financial crisis of 2007–08, and again in response to the COVID-19 pandemic.

Process and Benefits

Standard central bank monetary policies are usually enacted by buying or selling government bonds on the open market to reach a desired target for the interbank interest rate.  However, if a recession or depression continues even when a central bank has lowered interest rates to nearly zero, the central bank can no longer lower interest rates — a situation known as the liquidity trap.  The central bank may then implement quantitative easing by buying financial assets without reference to interest rates. This policy is sometimes described as a last resort to stimulate the economy.

A central bank enacts quantitative easing by purchasing, regardless of interest rates, a predetermined quantity of bonds or other financial assets on financial markets from private financial institutions.  This action increases the excess reserves that banks hold. The goal of this policy is to ease financial conditions, increase market liquidity, and encourage private bank lending.

Quantitative easing affects the economy through several channels:

• Credit channel: By providing liquidity in the banking sector, QE makes it easier and cheaper for banks to extend loans to companies and households, thus stimulating credit growth. Additionally, if the central bank also purchases financial instruments that are riskier than government bonds (such as corporate bonds), it can also increase the price and lower the interest yield of these riskier assets.
• Portfolio rebalancing: By enacting QE, the central bank withdraws an important part of the safe assets from the market onto its own balance sheet, which may result in private investors turning to other financial securities. Because of the relative lack of government bonds, investors are forced to "rebalance their portfolios" into other assets. Additionally, if the central bank also purchases financial instruments that are riskier than government bonds, it can also lower the interest yield of those assets (as those assets are more scarce in the market, and thus their prices go up correspondingly).
• Exchange rate: Because it increases the money supply and lowers the yield of financial assets, QE tends to depreciate a country's exchange rates relative to other currencies, through the interest rate mechanism.  Lower interest rates lead to a capital outflow from a country, thereby reducing foreign demand for a country's money, leading to a weaker currency. This increases demand for exports, and directly benefits exporters and export industries in the country.
• Fiscal effect: By lowering yields on sovereign bonds, QE makes it cheaper for governments to borrow on financial markets, which may empower the government to provide fiscal stimulus to the economy. Quantitative easing can be viewed as a debt refinancing operation of the "consolidated government" (the government including the central bank), whereby the consolidated government, via the central bank, retires government debt securities and refinances them into central bank reserves.
• Boosting asset prices: When a central bank buys government bonds from a pension fund, the pension fund, rather than hold on to this money, it might invest it in financial assets, such as shares, that gives it a higher return. And when demand for financial assets is high, the value of these assets increases. This makes businesses and households holding shares wealthier – making them more likely to spend more, boosting economic activity.
• Signalling effect: Some economists argue that QE's main impact is due to its effect on the psychology of the markets, by signalling that the central bank will take extraordinary steps to facilitate economic recovery. For instance, it has been observed that most of the effect of QE in the Eurozone on bond yields happened between the date of the announcement of QE and the actual start of the purchases by the ECB.

Effectiveness of QE

The effectiveness of quantitative easing is the subject of an intense dispute among researchers as it is difficult to separate the effect of quantitative easing from other contemporaneous economic and policy measures, such as negative rates.

Former Federal Reserve Chairman Alan Greenspan calculated that as of July 2012, there was "very little impact on the economy".  The straightforward reason was that little of the money ostensibly created by QE ever made it into circulation. Banks and other financial institutions simply re-deposited it in the Fed. Bank deposits in the Fed increased by nearly $4 trillion during QE1-3, closely tracking Fed bond purchases. The bond purchase program amounted to little more than an exercise in journal entry bookkeeping at the Fed. A different assessment has been offered by Federal Reserve Governor Jeremy Stein, who has said that measures of quantitive easing such as large-scale asset purchases "have played a significant role in supporting economic activity".

While the literature on the topic has grown over time, it has also been shown that central banks' own research on the effectiveness of quantitative easing tends to be optimistic in comparison to research by independent researchers, which could indicate a conflict of interest or cognitive bias in central bank research.

Several studies published in the aftermath of the crisis found that quantitative easing in the US has effectively contributed to lower long term interest rates on a variety of securities as well as lower credit risk. This boosted GDP growth and modestly increased inflation.  A predictable but unintended consequence of the lower interest rates was to drive investment capital into equities, thereby inflating the value of equities relative to the value of goods and services, and increasing the wealth gap between the wealthy and the working class.

In the Eurozone, studies have shown that QE successfully averted deflationary spirals in 2013-2014, and prevented the widening of bond yield spreads between member states.  QE also helped reduce bank lending cost.  However, the real effect of QE on GDP and inflation remained modest and very heterogeneous depending on methodologies used in research studies, which find on GDP comprised between 0.2% and 1.5% and between 0.1 and 1.4% on inflation. Model-based studies tend to find a higher impact than empirical ones.

Risks and Side-Effects of QE

Quantitative easing may cause higher inflation than desired if the amount of easing required is overestimated and too much money is created by the purchase of liquid assets.  On the other hand, QE can fail to spur demand if banks remain reluctant to lend money to businesses and households. Even then, QE can still ease the process of deleveraging as it lowers yields. However, there is a time lag between monetary growth and inflation; inflationary pressures associated with money growth from QE could build before the central bank acts to counter them.  Inflationary risks are mitigated if the system's economy outgrows the pace of the increase of the money supply from the easing.  If production in an economy increases because of the increased money supply, the value of a unit of currency may also increase, even though there is more currency available. For example, if a nation's economy were to spur a significant increase in output at a rate at least as high as the amount of debt monetized the inflationary pressures would be equalized. This can only happen if member banks actually lend the excess money out instead of hoarding the extra cash.  During times of high economic output, the central bank always has the option of restoring reserves to higher levels through raising interest rates or other means, effectively reversing the easing steps taken.

Economists such as John Taylor believe that quantitative easing creates unpredictability. Since the increase in bank reserves may not immediately increase the money supply if held as excess reserves, the increased reserves create the danger that inflation may eventually result when the reserves are loaned out.

QE benefits debtors, since the interest rate has fallen, meaning there is less money to be repaid. However, QE directly harms creditors as they earn less money from lower interest rates.  Devaluation of a currency also directly harms importers and consumers, as the cost of imported goods is inflated by the devaluation of the currency.

Impact on savings and pensions

In the European Union, World Pensions Council (WPC) financial economists have also argued that artificially low government bond interest rates induced by QE will have an adverse impact on the underfunding condition of pension funds, since "without returns that outstrip inflation, pension investors face the real value of their savings declining rather than ratcheting up over the next few years".  In addition to this, low or negative interest rates create disincentives for saving.  In a way this is an intended effect, since QE is intended to spur consumer spending.

Effects on climate change

In Europe, central banks operating corporate quantitative easing (i.e. QE programmes that include corporate bonds) such as the European Central Bank or the Swiss National Bank, have been increasingly criticized by NGOs for not taking into account the climate impact of the companies issuing the bonds.  In effect, Corporate QE programmes are perceived as indirect subsidy to polluting companies. The European Parliament has also joined the criticism by adopting several resolutions on the matter, and has repeatedly called on the ECB to reflect climate change considerations in its policies.

Central banks have usually responded by arguing they had to follow the principle of "market neutrality" and should therefore refrain from making discretionary choices when selecting bonds on the market. The notion that central banks can be market neutral is contested, as central banks always make choices that are not neutral for financial markets when implementing monetary policy.

However, in 2020, several top level ECB policymaker such as Christine Lagarde, Isabel Schnabel, Frank Elderson and others have pointed out the contradiction in the market neutrality logic. In particular, Schnabel argued that "In the presence of market failures, market neutrality may not be the appropriate benchmark for a central bank when the market by itself is not achieving efficient outcomes."

Since 2020, several central banks (including the ECB, Bank of England and the Swedish central banks) have announced their intention to incorporate climate criteria in their QE programmes.  The Network for Greening the Financial System has identified different possible measures to align central banks' collateral frameworks and QE with climate objectives.

Increased income and wealth inequality

Critics frequently point to the redistributive effects of quantitative easing. For instance, British Prime Minister Theresa May openly criticized QE in July 2016 for its regressive effects: "Monetary policy – in the form of super-low interest rates and quantitative easing – has helped those on the property ladder at the expense of those who can't afford to own their own home."  Dhaval Joshi of BCA Research wrote that "QE cash ends up overwhelmingly in profits, thereby exacerbating already extreme income inequality and the consequent social tensions that arise from it".  Anthony Randazzo of the Reason Foundation wrote that QE "is fundamentally a regressive redistribution program that has been boosting wealth for those already engaged in the financial sector or those who already own homes, but passing little along to the rest of the economy. It is a primary driver of income inequality".

Those criticisms are partly based on some evidence provided by central banks themselves. In 2012, a Bank of England report showed that its quantitative easing policies had benefited mainly the wealthy, and that 40% of those gains went to the richest 5% of British households.

In May 2013, Federal Reserve Bank of Dallas President Richard Fisher said that cheap money has made rich people richer, but has not done quite as much for working Americans.

Answering similar criticisms expressed by MEP Molly Scott Cato, the President of the ECB Mario Draghi once declared:

Some of these policies may, on the one hand, increase inequality but, on the other hand, if we ask ourselves what the major source of inequality is, the answer would be unemployment. So, to the extent that these policies help – and they are helping on that front – then certainly an accommodative monetary policy is better in the present situation than a restrictive monetary policy.

In July 2018, the ECB published a study showing that its QE programme increased the net wealth of the poorest fifth of the population by 2.5 percent, compared with just 1.0 percent for the richest fifth. The study's credibility was however contested.

International spillovers for BRICs and emerging economies

Quantitative easing (QE) policies can have a profound effect on Forex rates, since it changes the supply of one currency compared to another. For instance, if both the US and Europe are using quantitative easing to the same degree then the currency pair of US/EUR may not fluctuate. However, if the US treasury uses QE to a higher degree, as evidenced in the increased purchase of securities during an economic crisis, but India does not, then the value of the USD will decrease relative to the Indian rupee.  As a result, quantitative easing has the same effect as purchasing foreign currencies, effectively manipulating the value of one currency compared to another.

BRIC countries have criticized the QE carried out by the central banks of developed nations. They share the argument that such actions amount to protectionism and competitive devaluation.  As net exporters whose currencies are partially pegged to the dollar, they protest that QE causes inflation to rise in their countries and penalizes their industries.

In a joint statement leaders of Russia, Brazil, India, China and South Africa, collectively BRICS, have condemned the policies of western economies saying "It is critical for advanced economies to adopt responsible macro-economic and financial policies, avoid creating excessive liquidity and undertake structural reforms to lift growth" as written in the Telegraph.

According to Bloomberg reporter David Lynch, the new money from quantitative easing could be used by the banks to invest in emerging markets, commodity-based economies, commodities themselves, and non-local opportunities rather than to lend to local businesses that are having difficulty getting loans.

Moral hazard

Another criticism prevalent in Europe is that QE creates moral hazard for governments. Central banks’ purchases of government securities artificially depress the cost of borrowing. Normally, governments issuing additional debt see their borrowing costs rise, which discourages them from overdoing it. In particular, market discipline in the form of higher interest rates will cause a government like Italy's, tempted to increase deficit spending, to think twice. Not so, however, when the central bank acts as bond buyer of last resort and is prepared to purchase government securities without limit. In such circumstances, market discipline will be incapacitated.

Reputational risks

Richard W. Fisher, president of the Federal Reserve Bank of Dallas, warned in 2010 that QE carries "the risk of being perceived as embarking on the slippery slope of debt monetization.  We know that once a central bank is perceived as targeting government debt yields at a time of persistent budget deficits, concern about debt monetization quickly arises."  Later in the same speech, he stated that the Fed is monetizing the government debt: "The math of this new exercise is readily transparent: The Federal Reserve will buy $110 billion a month in Treasuries, an amount that, annualized, represents the projected deficit of the federal government for next year. For the next eight months, the nation's central bank will be monetizing the federal debt."

Ben Bernanke remarked in 2002 that the US government had a technology called the printing press (or, today, its electronic equivalent), so that if rates reached zero and deflation threatened, the government could always act to ensure deflation was prevented. He said, however, that the government would not print money and distribute it "willy nilly" but would rather focus its efforts in certain areas (e.g., buying federal agency debt securities and mortgage-backed securities).

According to economist Robert McTeer, former president of the Federal Reserve Bank of Dallas, there is nothing wrong with printing money during a recession, and quantitative easing is different from traditional monetary policy "only in its magnitude and pre-announcement of amount and timing".

             https://en.wikipedia.org/wiki/Quantitative_easing

See also the Daily Quiddity entry for December 19, 2013.

New Algorithm Flies Drones Faster than Human Racing Pilots Can

For the first time an autonomously flying quadrotor has outperformed two human pilots in a drone race. The success is based on a novel algorithm that calculates time-optimal trajectories that fully consider the drones' limitations.

From:  University of Zurich

July 21, 2021 -- To be useful, drones need to be quick. Because of their limited battery life they must complete whatever task they have -- searching for survivors on a disaster site, inspecting a building, delivering cargo -- in the shortest possible time. And they may have to do it by going through a series of waypoints like windows, rooms, or specific locations to inspect, adopting the best trajectory and the right acceleration or deceleration at each segment.

Algorithm outperforms professional pilots

The best human drone pilots are very good at doing this and have so far always outperformed autonomous systems in drone racing. Now, a research group at the University of Zurich (UZH) has created an algorithm that can find the quickest trajectory to guide a quadrotor -- a drone with four propellers -- through a series of waypoints on a circuit. "Our drone beat the fastest lap of two world-class human pilots on an experimental race track," says Davide Scaramuzza, who heads the Robotics and Perception Group at UZH and the Rescue Robotics Grand Challenge of the NCCR Robotics, which funded the research.

"The novelty of the algorithm is that it is the first to generate time-optimal trajectories that fully consider the drones' limitations," says Scaramuzza. Previous works relied on simplifications of either the quadrotor system or the description of the flight path, and thus they were sub-optimal. "The key idea is, rather than assigning sections of the flight path to specific waypoints, that our algorithm just tells the drone to pass through all waypoints, but not how or when to do that," adds Philipp Foehn, PhD student and first author of the paper.

External cameras provide position information in real-time

The researchers had the algorithm and two human pilots fly the same quadrotor through a race circuit. They employed external cameras to precisely capture the motion of the drones and -- in the case of the autonomous drone -- to give real-time information to the algorithm on where the drone was at any moment. To ensure a fair comparison, the human pilots were given the opportunity to train on the circuit before the race. But the algorithm won: all its laps were faster than the human ones, and the performance was more consistent. This is not surprising, because once the algorithm has found the best trajectory it can reproduce it faithfully many times, unlike human pilots.

Before commercial applications, the algorithm will need to become less computationally demanding, as it now takes up to an hour for the computer to calculate the time-optimal trajectory for the drone. Also, at the moment, the drone relies on external cameras to compute where it was at any moment. In future work, the scientists want to use onboard cameras. But the demonstration that an autonomous drone can in principle fly faster than human pilots is promising. "This algorithm can have huge applications in package delivery with drones, inspection, search and rescue, and more," says Scaramuzza.

        https://www.sciencedaily.com/releases/2021/07/210721142013.htm 

Afghanistan Suicide Bombing

On 26 August 2021 at 17:50 local time (13:20 UTC), during the evacuation from Afghanistan, a suicide bombing occurred near Abbey Gate at Hamid Karzai International Airport in Kabul, Afghanistan.  At least 170 people were killed in the attacks, including 13 members of the United States military, who were the first American military casualties in Afghanistan since February 2020.

Background

After Afghanistan fell to Taliban control on 15 August 2021, Hamid Karzai International Airport became the only secure way out of Afghanistan.  Security concerns grew after hundreds of members of the Islamic State of Iraq and the Levant – Khorasan Province (ISIS-K) escaped from jails at Bagram and Pul-e-Charkhi.  Hours before the attack, US diplomats in Kabul warned American citizens to leave the airport because of security threats.  United Kingdom Armed Forces Minister James Heappey had also warned of a highly credible threat of attack at Kabul airport by Islamic State militants.  Embassies from United States, United Kingdom, and Australia also warned about high security threats on the airport.

US President Joe Biden reportedly received multiple reports of a possible attack during the week preceding the attack.

Attack

Amid the 2021 evacuation of Afghanistan, a crowd of local and foreign civilians had fled to the airport to evacuate.  At Abbey Gate, one of the gates leading into the airport, a suicide bomber detonated an explosive.  After the explosion, gunfire erupted, and all gates to the airport were closed.  

An eye witness to the explosion stated it occurred by a canal with American forces on one side; checking evacuees passports, visas and other documentation before allowing them inside the airport. Another stated that the explosion felt as if someone pulled the ground from under his feet, and saw other evacuees thrown in the air by the force of the blast.

Victims

At least 170 people were killed during the attack, including at least 62 Afghan civilians, 28 Taliban members, 13 US service members, two British nationals and the child of a third British national.

At least 200 more people were injured, including 18 US military personnel and more Taliban members.  The dead Americans were identified as ten marines, two soldiers, and one Navy corpsman.  The US deaths were the first US service deaths in Afghanistan since February 2020 and were the largest single loss of life of US military personnel since the 2011 Afghanistan Boeing Chinook shootdown.

Responsibility

The attack was carried out by ISIL-K, who released a statement in which they claimed responsibility for the attack and named the suicide bomber.

ISIS-K reportedly has strong connections with the Haqqani network, which is linked to the Taliban. ISIS-K and the Taliban are, however, enemies that have been involved in a long, deadly conflict.  The leader of the Haqqani network, Khalil Haqqani, is currently in charge of security in Kabul.  A number of ISIS-K militants were reportedly released by the Taliban on 15 August from Pul-e-Charkhi prison, along with all the other prisoners there.

Reactions

Through a tweet by their spokesperson, the Taliban condemned the attack, saying "evil circles will be strictly stopped".

Abdullah Abdullah, former Chief Executive of Afghanistan and current National Coalition of Afghanistan leader, condemned the attack.  Some civilians claimed to reporters that the attacks had strengthened their resolve to evacuate from the country in fear of more attacks.

U.S. President Joe Biden made a public address following the attacks. He honored the American service members who were killed in the attacks, calling them "heroes" and saying they lost their lives "in the service of liberty", and stated that the U.S. had evacuated more than 100,000 Americans, Afghans, and others. He expressed deep sorrow for the Afghan victims as well. Biden said to those who wished harm upon the US that "we will hunt you down and make you pay."  The government of the United Kingdom also said that they will continue Operation Pitting, the evacuation from Afghanistan.

Many nations expressed condemnation for the Kabul airport attacks and solidarity with the victims and troops conducting evacuations at the airport.  The European Commission and the United Nations likewise condemned the attacks. German Chancellor Angela Merkel cancelled an upcoming trip to Israel, and will stay in Germany to monitor the evacuation of German troops.  Biden also rescheduled a meeting with visiting Israeli Prime Minister Naftali Bennett because of the attacks.  The United Kingdom said civilian evacuations would continue in spite of the attacks.

                    https://en.wikipedia.org/wiki/2021_Kabul_airport_attack 

Rechargeable Batteries that Store Six Times the Charge of Lithium-Ion in Current Use

A new type of rechargeable alkali metal-chlorine battery developed at Stanford holds six times more electricity than the commercially available rechargeable lithium-ion batteries commonly used today.

By Andrew Myers for Stanford News Service

August 25, 2021 -- An international team of researchers led by Stanford University has developed rechargeable batteries that can store up to six times more charge than ones that are currently commercially available.

The advance, detailed in a new paper published Aug. 25 in the journal Nature, could accelerate the use of rechargeable batteries and puts battery researchers one step closer toward achieving two top stated goals of their field: creating a high-performance rechargeable battery that could enable cellphones to be charged only once a week instead of daily and electric vehicles that can travel six times farther without a recharge.

The new so-called alkali metal-chlorine batteries, developed by a team of researchers led by Stanford chemistry Professor Hongjie Dai and doctoral candidate Guanzhou Zhu, relies on the back-and-forth chemical conversion of sodium chloride (Na/Cl₂) or lithium chloride (Li/Cl₂) to chlorine.

When electrons travel from one side of a rechargeable battery to the other, recharging reverts the chemistry back to its original state to await another use. Non-rechargeable batteries have no such luck. Once drained, their chemistry cannot be restored.

“A rechargeable battery is a bit like a rocking chair. It tips in one direction, but then rocks back when you add electricity,” Dai explained. “What we have here is a high-rocking rocking chair.”

Serendipitous Discovery

The reason no one had yet created a high-performance rechargeable sodium-chlorine or lithium-chlorine battery is that chlorine is too reactive and challenging to convert back to a chloride with high efficiency. In the few cases where others were able to achieve a certain degree of rechargeability, the battery performance proved poor.

In fact, Dai and Zhu did not set out to create a rechargeable sodium and lithium-chlorine battery at all, but merely to improve their existing battery technologies using thionyl chloride. This chemical is one of the main ingredients of lithium-thionyl chloride batteries, which are a popular type of single-use battery first invented in the 1970s.

But in one of their early experiments involving chlorine and sodium chloride, the Stanford researchers noticed that the conversion of one chemical to another had somehow stabilized, resulting in some rechargeability. “I didn’t think it was possible,” Dai said. “It took us about at least a year to really realize what was going on.”

Over the next several years, the team elucidated the reversible chemistries and sought ways to make it more efficient by experimenting with many different materials for the battery’s positive electrode. The big breakthrough came when they formed the electrode using an advanced porous carbon material from collaborators Professor Yuan-Yao Li and his student Hung-Chun Tai from the National Chung Cheng University of Taiwan. The carbon material has a nanosphere structure filled with many ultra-tiny pores. In practice, these hollow spheres act like a sponge, sopping up copious amounts of otherwise touchy chlorine molecules and storing them for later conversion to salt inside the micropores.

“The chlorine molecule is being trapped and protected in the tiny pores of the carbon nanospheres when the battery is charged,” Zhu explained. “Then, when the battery needs to be drained or discharged, we can discharge the battery and convert chlorine to make NaCl – table salt – and repeat this process over many cycles. We can cycle up to 200 times currently and there’s still room for improvement.”

The result is a step toward the brass ring of battery design – high energy density. The researchers have so far achieved 1,200 milliamp hours per gram of positive electrode material, while the capacity of commercial lithium-ion battery today is up to 200 milliamp hours per gram. “Ours has at least six times higher capacity,” Zhu said.

The researchers envision their batteries one day being used in situations where frequent recharging is not practical or desirable, such as in satellites or remote sensors. Many otherwise usable satellites are now floating in orbit, obsolete due to their dead batteries. Future satellites equipped with long-lived rechargeable batteries could be fitted with solar chargers, extending their usefulness many times over.

For now though, the working prototype they’ve developed might still be suitable for use in small everyday electronics like hearing aids or remote controls. For consumer electronics or electrical vehicles, much more work remains to engineer the battery structure, increase the energy density, scale up the batteries and increase the number of cycles.

Hongjie Dai is the J. G. Jackson and C. J. Wood Professor in Chemistry in the School of Humanities and Sciences. Additional researchers at Stanford are Xin Tian, Jiachen Li, Hao Sun, Peng Liang, Michael Angell and Yongtao Meng. Additional co-authors are from National Chung Cheng University, National Synchrotron Radiation Research Center, National Central University, National Taiwan University of Science & Technology – all in Taiwan; as well as Shandong University of Science & Technology in China. This research was supported by Stanford’s Bits & Watts Initiative and employed tools at the Stanford Nano Shared Facilities, which is supported by the National Science Foundation.

               https://news.stanford.edu/press/view/40872

Raising the Steaks in Japan: First 3D-Bioprinted Structured Wagyu Beef-Like Meat Unveiled

 Raising the Steaks in Japan: First 3D-Bioprinted Structured Wagyu Beef-Like Meat Unveiled

Researchers at Osaka University use 3D-bioprinting to create structured cultured meat like the complex texture of Wagyu beef, which may provide an environmentally friendly and sustainable method for producing cultured meat alternatives

From:  Osaka University

Osaka, Japan – August 24, 2021 -- Scientists from Osaka University used stem cells isolated from Wagyu cows to 3D-print a meat alternative containing muscle, fat, and blood vessels arranged to closely resemble conventional steaks. This work may help usher in a more sustainable future with widely available cultured meat. Wagyu can be literally translated into “Japanese cow,” and is famous around the globe for its high content of intramuscular fat, known as marbling or sashi. This marbling provides the beef its rich flavors and distinctive texture. However, the way cattle are raised today is often considered to be unsustainable in light of its outsized contribution to climate emissions. Currently, the available “cultured meat” alternatives only consist primarily of poorly organized muscle fiber cells that fail to reproduce the complex structure of real beef steaks.

Now, a team of scientists led by Osaka University have used 3D-Printing to create synthetic meat that looks more like the real thing. “Using the histological structure of Wagyu beef as a blueprint, we have developed a 3D-printing method that can produce tailor-made complex structures, like muscle fibers, fat, and blood vessels,” lead author Dong-Hee Kang says. To overcome this challenge, the team started with two types of stem cells, called bovine satellite cells and adipose-derived stem cells. Under the right laboratory conditions, these “multipotent” cells can be coaxed to differentiate into every type of cell needed to produce the cultured meat.

Individual fibers including muscle, fat, or blood vessels were fabricated from these cells using bioprinting. The fibers were then arranged in 3D, following the histological structure, to reproduce the structure of the real Wagyu meat, which was finally sliced perpendicularly, in a similar way to the traditional Japanese candy Kintaro-ame. This process made the reconstruction of the complex meat tissue structure possible in a customizable manner. “By improving this technology, it will be possible to not only reproduce complex meat structures, such as the beautiful sashi of Wagyu beef, but to also make subtle adjustments to the fat and muscle components,” senior author Michiya Matsusaki says. That is, customers would be able to order cultured meat with their desired amount of fat, based on taste and health considerations.

                https://www.eurekalert.org/news-releases/926245

 

Stinkweed As a Cleaner Bio-Jet Fuel

A common farm weed could make a 'greener' jet fuel with fewer production-related environmental impacts than other biofuels, a new study indicates.

From:  Ohio State University

August 2, 2021 -- Growing the weed, pennycress -- often called stinkweed -- as a crop requires less fertilizer and fewer pesticides than other plants that can be used to make renewable jet fuel, according to the study. Pennycress also requires fewer farm operations, such as soil tilling, than other potential biofuel crops, reducing the associated environmental costs. Those costs include carbon dioxide emissions that cause the climate to change, as well as other emissions that pollute the air.

Environmental impacts could be further mitigated through farm management techniques that keep fertilizer on fields, rather than allowing it to run off into nearby watersheds, the study suggests. Such techniques can add to the financial cost of growing crops, but reduce their environmental footprints.

"Reducing greenhouse gas emissions from air travel will mean not just incremental changes, but a fundamental change in how we have been producing fuel and where that fuel comes from," said Ajay Shah, senior author of the study and associate professor of food, agricultural and biological engineering at The Ohio State University in Wooster. "And what we found is that pennycress might make a very good alternative fuel, especially when you consider the environmental costs of producing it."

The study was published recently online in the journal Applied Energy.

For this study, the researchers estimated the environmental impacts of growing pennycress, transporting it to a biorefinery and converting it to a usable jet fuel. They also accounted for the environmental costs of burning leftover byproducts of refining the pennycress seed into fuel.

Those environmental costs include fertilizer and pesticide use, water consumption and the energy required to harvest and transport pennycress seeds from a farm to a biorefinery and process them into usable fuel.

The researchers built computer models to determine how much total energy it would take to produce jet fuel from pennycress seeds and compared those estimates with the energy needed for producing biofuels from other crops. The data for the models came from existing studies about biofuel production.

Their models showed that it took about half as much energy to produce jet fuel from pennycress as it did to produce jet fuel from canola or sunflowers, two other potential bio-jet fuel crops. Pennycress oil production used about a third as much energy as soybean oil production, the researchers found, and the energy needed for turning pennycress into jet fuel was about the same as that used to produce fuel from the flowering plant camelina, another biofuel crop.

Renewable jetfuels are not yet financially competitive with fossil fuel-based fuels, Shah said. But calculating the environmental impacts of alternative bio-based fuels should help both farmers and policymakers as they try to limit carbon dioxide in the Earth's atmosphere and, hopefully, to slow or stop climate change.

"Pennycress also makes an appealing alternative jet fuel because of its growing season," Shah said. "It is a winter cover crop that can be grown between corn season and soybean season, giving the same body of farmland an extra production cycle each year.

"Pennycress can be planted when corn is still standing in the field, before the corn harvest," he said. "And it can be harvested before the soybean crops are planted. The bottom line is it can be used as a cover crop, it doesn't divert any agricultural production land, and it has suitable properties for renewable jet fuel production."

Greenhouse gas emissions from air travel contribute to climate change, accounting for about 2% of all human-induced carbon-dioxide emissions, according to various groups that study the effects of transportation on climate change.

"Reducing those emissions will almost certainly mean finding cleaner alternatives to jet fuels made from fossil fuels," Shah said. "Studies like this one can help determine the best alternative.

"When it comes to pennycress, production and logistics are the big contributors to both the environmental impacts and the costs, and those are the challenge areas - they have to be streamlined and solved to make it more efficient," he said. "If we could improve those areas, we could make production more energy-efficient and substantially lower the costs and environmental impacts."

This work was supported by funding from the U.S. Department of Energy.

              https://www.sciencedaily.com/releases/2021/08/210802114945.htm

Evidence of Solar-Driven Change on the Moon

PhD student discovers that solar radiation could be a more important source of lunar iron nanoparticles than previously thought

By Heather Tate, Northern Arizona University

August 20, 2021 -- Tiny iron nanoparticles unlike any found naturally on Earth are nearly everywhere on the Moon—and scientists are trying to understand why. A new study led by Northern Arizona University doctoral candidate Christian J. Tai Udovicic, in collaboration with associate professor Christopher Edwards, both of NAU’s Department of Astronomy and Planetary Science, uncovered important clues to help understand the surprisingly active lunar surface. In an article recently published in Geophysical Research Letters, the scientists found that solar radiation could be a more important source of lunar iron nanoparticles than previously thought.

Asteroid impacts and solar radiation affect the Moon in unique ways because it lacks the protective magnetic field and atmosphere that protect us here on Earth. Both asteroids and solar radiation break down lunar rocks and soil, forming iron nanoparticles (some smaller, some larger) that are detectable from instruments on satellites orbiting the Moon. The study used data from National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA) spacecraft to understand how quickly iron nanoparticles form on the Moon over time.

“We have thought for a long time that the solar wind has a small effect on lunar surface evolution, when in fact it may be the most important process producing iron nanoparticles,” Tai Udovicic said. “Since iron absorbs a lot of light, very small amounts of these particles can be detected from very far away – making them a great indicator of change on the Moon”.

Surprisingly, the smaller iron nanoparticles seemed to form at a similar rate as radiation damage in samples returned from the Apollo missions to the Moon, a hint that the Sun has a strong influence in their formation.

“When I saw the Apollo sample data and our satellite data side by side for the first time, I was shocked,” Tai Udovicic said. “This study shows that the solar radiation could have a much larger influence in active change on the Moon than previously thought, not only darkening its surface, but it might also create small quantities of water usable in future missions.”

As NASA prepares to land the first woman and the next man on the surface of the Moon by 2024 as part of the Artemis mission, understanding the solar radiation environment and possible resources on the Moon are critical. In future work recently awarded a NASA Future Investigators in Space Science and Technology (FINESST) grant, Tai Udovicic plans to broaden his targeted study to the entire Moon, but is also eager to take a closer look at mysterious lunar swirls, one of which was recently selected as a landing site for the upcoming Lunar Vertex rover. He also studies lunar temperatures and water ice stability to inform future missions.

“This work helps us understand, from a bird’s eye view, how the lunar surface changes over time,” said Tai Udovicic. “While there is still a lot to learn, we want to make sure that when we have boots back on the Moon, that those missions are backed by the best science available. It’s the most exciting time to be a lunar scientist since the tail end of the Apollo era in the 70s.”

              https://nau.edu/nau-research/change_on_moon/ 

Coming: Use of Artificial Intelligence for Early Detection and Treatment of Illnesses

Artificial intelligence (AI) will fundamentally change medicine and healthcare: Diagnostic patient data, e.g. from ECG, EEG or X-ray images, can be analyzed with the help of machine learning, so that diseases can be detected at a very early stage based on subtle changes

From:  Technische Universität Dresden

August 20, 2021 -- However, implanting AI within the human body is still a major technical challenge. TU Dresden scientists at the Chair of Optoelectronics have now succeeded for the first time in developing a bio-compatible implantable AI platform that classifies in real time healthy and pathological patterns in biological signals such as heartbeats. It detects pathological changes even without medical supervision. The research results have now been published in the journal Science Advances.

In this work, the research team led by Prof. Karl Leo, Dr. Hans Kleemann and Matteo Cucchi demonstrates an approach for real-time classification of healthy and diseased bio-signals based on a biocompatible AI chip. They used polymer-based fiber networks that structurally resemble the human brain and enable the neuromorphic AI principle of reservoir computing. The random arrangement of polymer fibers forms a so-called "recurrent network," which allows it to process data, analogous to the human brain. The nonlinearity of these networks enables to amplify even the smallest signal changes, which -- in the case of the heartbeat, for example -- are often difficult for doctors to evaluate. However, the nonlinear transformation using the polymer network makes this possible without any problems.

In trials, the AI was able to differentiate between healthy heartbeats from three common arrhythmias with an 88% accuracy rate. In the process, the polymer network consumed less energy than a pacemaker. The potential applications for implantable AI systems are manifold: For example, they could be used to monitor cardiac arrhythmias or complications after surgery and report them to both doctors and patients via smartphone, allowing for swift medical assistance.

"The vision of combining modern electronics with biology has come a long way in recent years with the development of so-called organic mixed conductors," explains Matteo Cucchi, PhD student and first author of the paper. "So far, however, successes have been limited to simple electronic components such as individual synapses or sensors. Solving complex tasks has not been possible so far. In our research, we have now taken a crucial step toward realizing this vision. By harnessing the power of neuromorphic computing, such as reservoir computing used here, we have succeeded in not only solving complex classification tasks in real time but we will also potentially be able to do this within the human body. This approach will make it possible to develop further intelligent systems in the future that can help save human lives."

          https://www.sciencedaily.com/releases/2021/08/210820135346.htm 

Basics of the COVID-19 Pandemic

The ongoing global pandemic of coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was identified in Wuhan, China, in December 2019; a lockdown in Wuhan and other cities in Hubei province failed to contain the outbreak, and it spread to other parts of mainland China and around the world. The World Health Organization (WHO) declared a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020. Since 2021, variants of the virus have emerged or become dominant in many countries, with the Delta, Alpha and Beta variants being the most virulent.  As of 21 August 2021, more than 211 million cases and 4.42 million deaths have been confirmed, making it one of the deadliest pandemics in history.

COVID-19 symptoms range from unnoticeable to life-threatening. Severe illness is more likely in elderly patients, as well as those who have certain underlying medical conditions.  The disease transmits when people breathe in air contaminated by droplets and small airborne particles.  The risk of breathing these in is highest when people are in close proximity, but still present over longer distances, particularly indoors. Transmission can also occur if splashed or sprayed with contaminated fluids in the eyes, nose, or mouth, and, rarely, via contaminated surfaces. People remain contagious for up to 20 days, and can spread the virus even if they do not develop any symptoms.

Recommended preventive measures include social distancing, wearing face masks in public, ventilation and air-filtering, hand washing, covering one's mouth when sneezing or coughing, disinfecting surfaces, and monitoring and self-isolation for people exposed or symptomatic.  Several vaccines have been distributed in many countries since December 2020.  Treatments focus on addressing symptoms, but work is underway to develop medications that inhibit the virus. Authorities worldwide have responded by implementing travel restrictions, lockdowns and quarantines, workplace hazard controls, and business closures. There are also efforts to increase testing capacity and trace contacts of the infected.

The pandemic has resulted in severe global social and economic disruption, including the largest global recession since the Great Depression of the 1930s.  It has led to widespread supply shortages exacerbated by panic buying, agricultural disruption, food shortages, and decreased emissions of pollutants.  Numerous educational institutions and public areas have been partially or fully closed, and many events have been cancelled or postponed.  Misinformation has circulated through social media and mass media, and political tensions have been exacerbated. The pandemic has raised issues of racial and geographic discrimination, health equity, and the balance between public health imperatives and individual rights.

Background

Although the exact origin of the virus is still unknown, the first outbreak started in Wuhan, Hubei, China in November 2019. Many early cases of COVID-19 were linked to people who had visited the Huanan Seafood Wholesale Market in Wuhan, but it is possible that human-to-human transmission was already happening before this.  On 11 February 2020, the World Health Organization (WHO) named the disease "COVID-19", which is short for coronavirus disease 2019.  The virus that caused the outbreak is known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a newly discovered virus closely related to bat coronaviruses, pangolin coronaviruses, and SARS-CoV.  The scientific consensus is that the virus is most likely of zoonotic origin, from bats or another closely-related mammal.  Despite this, the subject has generated a significant amount of speculation and conspiracy theories, which were amplified by rapidly growing online echo chambers.  Global geopolitical divisions, notably between the United States and China, have bee0n heightened because of this issue.

The earliest known person with symptoms was later discovered to have fallen ill on 1 December 2019, and that person did not have visible connections with the later wet market cluster.  However, an earlier case of infection could have occurred on 17 November.  Of the early cluster of cases reported that month, two-thirds were found to have a link with the market.  Molecular clock analysis suggests that the index case is likely to have been infected with the virus between mid-October and mid-November 2019.

Cases of COVID-19

Official case counts refer to the number of people who have been tested for COVID-19 and whose test has been confirmed positive according to official protocols.  Many countries, early on, had official policies to not test those with only mild symptoms.  An analysis of the early phase of the outbreak up to 23 January estimated 86 per cent of COVID-19 infections had not been detected, and that these undocumented infections were the source for 79 per cent of documented cases.  Several other studies, using a variety of methods, have estimated that numbers of infections in many countries are likely to be considerably greater than the reported cases.

On 9 April 2020, preliminary results found that 15 per cent of people tested in Gangelt, the centre of a major infection cluster in Germany, tested positive for antibodies.  Screening for COVID-19 in pregnant women in New York City, and blood donors in the Netherlands, has also found rates of positive antibody tests that may indicate more infections than reported.  Seroprevalence based estimates are conservative as some studies show that persons with mild symptoms do not have detectable antibodies.  Some results (such as the Gangelt study) have received substantial press coverage without first passing through peer review.

An analysis in early 2020 of cases by age in China indicated that a relatively low proportion of cases occurred in individuals under 20.  It was not clear whether this was because young people were less likely to be infected, or less likely to develop serious symptoms and seek medical attention and be tested.  A retrospective cohort study in China found that children and adults were just as likely to be infected.

Initial estimates of the basic reproduction number (R₀) for COVID-19 in January were between 1.4 and 2.5, but a subsequent analysis concluded that it may be about 5.7 (with a 95 per cent confidence interval of 3.8 to 8.9).  R₀ can vary across populations and is not to be confused with the effective reproduction number (commonly just called R), which takes into account effects such as social distancing and herd immunity.  By mid-May 2020, the effective R was close to or below 1.0 in many countries, meaning the spread of the disease in these areas at that time was stable or decreasing.

Deaths

Official deaths from COVID-19 generally refer to people who died after testing positive according to protocols. These counts may ignore deaths of people who die without having been tested.  Conversely, deaths of people who had underlying conditions may lead to over-counting.  Comparisons of statistics for deaths for all causes versus the seasonal average indicate excess mortality in many countries.  This may include deaths due to strained healthcare systems and bans on elective surgery.  The first confirmed death was in Wuhan on 9 January 2020.  Nevertheless, the first reported death outside of China occurred on 1 February 2020 in the Philippines, and the first reported death outside Asia was in the United States on 6 February 2020.

More than 95 per cent of the people who contract COVID-19 recover. Otherwise, the time between symptoms onset and death usually ranges from 6 to 41 days, typically about 14 days.  As of 21 August 2021, more than 4.42 million deaths have been attributed to COVID-19. People at the greatest risk of mortality from COVID-19 tend to be those with underlying conditions, such as those with a weakened immune system, serious heart or lung problems, severe obesity, or the elderly (including individuals age 65 years or older).

Multiple measures are used to quantify mortality.  These numbers vary by region and over time, influenced by testing volume, healthcare system quality, treatment options, government response, time since the initial outbreak, and population characteristics, such as age, sex, and overall health.  Countries like Belgium include deaths from suspected cases of COVID-19, regardless of whether the person was tested, resulting in higher numbers compared to countries that include only test-confirmed cases.

The death-to-case ratio reflects the number of deaths attributed to COVID-19 divided by the number of diagnosed cases within a given time interval. Based on Johns Hopkins University statistics, the global death-to-case ratio is 2.09 percent (4,420,984 deaths for 211,232,169 cases) as of 21 August 2021.  The number varies by region.

Signs and Symptoms

Symptoms of COVID-19 are variable, ranging from mild symptoms to severe illness.  Common symptoms include headache, loss of smell and taste, nasal congestion and runny nose, cough, muscle pain, sore throat, fever, diarrhea, and breathing difficulties.  People with the same infection may have different symptoms, and their symptoms may change over time. Three common clusters of symptoms have been identified: one respiratory symptom cluster with cough, sputum, shortness of breath, and fever; a musculoskeletal symptom cluster with muscle and joint pain, headache, and fatigue; a cluster of digestive symptoms with abdominal pain, vomiting, and diarrhea.  In people without prior ear, nose, and throat disorders, loss of taste combined with loss of smell is associated with COVID-19.

Of people who show symptoms, 81% develop only mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging) and 5% of patients suffer critical symptoms (respiratory failure, shock, or multiorgan dysfunction).  At least a third of the people who are infected with the virus do not develop noticeable symptoms at any point in time.  These asymptomatic carriers tend not to get tested and can spread the disease.  Other infected people will develop symptoms later, called "pre-symptomatic", or have very mild symptoms and can also spread the virus.

As is common with infections, there is a delay between the moment a person first becomes infected and the appearance of the first symptoms. The median delay for COVID-19 is four to five days.  Most symptomatic people experience symptoms within two to seven days after exposure, and almost all will experience at least one symptom within 12 days.

Most people recover from the acute phase of the disease. However, some people – over half of a cohort of home-isolated young patients – continue to experience a range of effects, such as fatigue, for months after recovery, a condition called long COVID; long-term damage to organs has been observed. Multi-year studies are underway to further investigate the long-term effects of the disease.

               https://en.wikipedia.org/wiki/COVID-19_pandemic