The Social History of Viruses

Introduction

By the Blog Author

Rabies, dengue fever, yellow fever, polio, smallpox (now extinguished worldwide), measles, influenza and HIV are all viral diseases. Certain viruses carry genetic material from one species to another. Viruses are particularly common in the oceans, where they remain largely unstudied. Below is a very brief excerpt from a long article in Wikipedia about the social history of viruses.

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The social history of viruses describes the influence of viruses and viral infections on human history.
Epidemics caused by viruses began when human behaviour changed during the Neolithic period. Having been hunter-gatherers, humans developed more densely populated agricultural communities, which allowed viruses to spread rapidly and subsequently to become endemic. Viruses of plants and livestock also increased, and as humans became dependent on agriculture and farming, diseases such as potyviruses of potatoes and rinderpest of cattle had devastating consequences.

Smallpox and measles viruses are among the oldest that infect humans. Having evolved from viruses that infected animals, they first appeared in humans in Europe and North Africa thousands of years ago. The viruses were later carried to the New World by Europeans during the time of the Spanish Conquests, but the indigenous people had no natural resistance to the viruses and thousands of them died during epidemics. Influenza pandemics have been recorded since 1580, and they have occurred with increasing frequency in subsequent centuries. The pandemic of 1918-19, in which 40–50 million died in less than a year was one of the most devastating in history.

Louis Pasteur and Edward Jenner were the first to develop vaccines to protect against viral infections. The nature of viruses remained unknown until the invention of the electronic microscope in the 1930s, when the science of virology gained momentum. In the 20th century many diseases both old and new were found to be caused by viruses. There were epidemics of poliomyelitis that were only controlled following the development of a vaccine in the 1950s. HIV is the most pathogenic new virus to have emerged in centuries. Although scientific interest in them arose because of the diseases they cause, viruses can be beneficial, driving evolution by transferring genes across species and playing important roles in ecosystems.

Friendly Viruses
Sir Peter Medawar (1915–1987) described a virus as "a piece of bad news wrapped in a protein coat". With the exception of the bacteriophages, viruses had a well-deserved reputation for being nothing but the cause of diseases and death. The discovery of the abundance of viruses and their overwhelming presence in many ecosystems has led modern virologists to reconsider their role in the biosphere.

It is estimated that there are about 10³¹ (100 billion trillion) viruses on Earth. Most of them are bacteriophages, and most are in the oceans. Microorganisms constitute more than 90 per cent of the biomass in the sea, and it has been estimated that viruses kill approximately 20 per cent of this biomass each day and that there are fifteen times as many viruses in the oceans as there are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms, which often kill other marine life, and help maintain the ecological balance of different species of marine blue-green algae, and thus adequate oxygen production for life on Earth.

The emergence of strains of bacteria that are resistant to a broad range of antibiotics has become a problem in the treatment of bacterial infections. Only two new classes of antibiotics have been developed in the past 30 years, and novel ways of combating bacterial infections are being sought. Bacteriophages were first used to control bacteria in the 1920s, and a large clinical trial was conducted by Soviet scientists in 1963. This work was unknown outside the Soviet Union until the results of the trial were published in the West in 1989. The recent and escalating problems caused by antibiotic-resistant bacteria has stimulated a renewed interest in the use of bacteriophages and phage therapy.

The Human Genome Project has revealed the presence of numerous viral DNA sequences scattered throughout the human genome. These sequences make up around eight per cent of human DNA, and appear to be the remains of ancient retrovirus infections of human ancestors. These pieces of DNA have firmly established themselves in human DNA. Most of this DNA is no longer functional, but some of these friendly viruses have brought with them novel genes that are important in human development. Viruses have transferred important genes to plants. About ten per cent of all photosynthesis uses the products of genes that have been transferred to plants from blue-green algae by viruses.

This and much more available at this link:

http://en.wikipedia.org/wiki/Social_history_of_viruses