Friday, March 11, 2016

Zika Virus Outbreak

As of early 2016, a widespread outbreak of Zika fever, caused by the Zika virus, is ongoing, primarily in the Americas. The outbreak began in April 2015 in Brazil, and has spread to other countries in South America, Central America, Mexico, and the Caribbean. Brazilian researchers have suggested that the Zika virus arrived during the 2014 FIFA World Cup tournament.  In January 2016, the World Health Organization (WHO) said the virus was likely to spread throughout most of the Americas by the end of the year; and in February 2016, the WHO declared the cluster of microcephaly and Guillain–Barré syndrome (GBS) cases reported in Brazil – strongly suspected to be associated with the Zika virus outbreak – a Public Health Emergency of International Concern.

                                                        Cases Since 2015 in Purple

The virus is spread mainly by the Aedes aegypti mosquito, which is commonly found throughout the tropical and subtropical Americas. It can also be spread by the Aedes albopictus ("Asian tiger") mosquito, which has become widespread as far north as the Great Lakes region in North America. Sexual transmission of the Zika virus is also possible. Most Zika virus infections are asymptomatic, rendering precise estimates of the number of cases difficult to determine. In approximately one in five cases, Zika virus infections result in Zika fever, a minor illness that causes symptoms such as fever and a rash. Critically, Zika virus infections of pregnant women have a suspected link with newborn microcephaly by mother-to-child transmission. In addition, Zika is suspected of being associated with a cluster of cases of Guillain–Barré syndrome.

A number of countries have issued travel warnings, and the outbreak is expected to significantly impact the tourism industry. Several countries have taken the unusual step of advising their citizens to delay pregnancy until more is known about the virus and its impact on fetal development.

Possible Link to Infant Microcephaly and other Disorders

On 1 February 2016, the World Health Organization declared recently reported clusters of microcephaly and other neurological disorders a Public Health Emergency of International Concern (PHEIC).

                                                           Microcephaly shown at left

The Zika virus was first linked with newborn microcephaly during the Brazil Zika virus outbreak. In 2015, there were 2,782 cases of microcephaly compared with 147 in 2014 and 167 in 2013. Confirmation of many of the recent cases is pending, and it is difficult to estimate how many cases went unreported before the recent awareness of the risk of virus infections.

In November 2015, the Zika virus was isolated in a newborn baby from the northeastern state of Ceará, Brazil, with microcephaly and other congenital disorders. The Lancet medical journal reported in January 2016 that the Brazilian Ministry of Health had confirmed 134 cases of microcephaly "believed to be associated with Zika virus infection" with an additional 2,165 cases in 549 counties in 20 states remaining under investigation.

In January 2016, a baby in Oahu, Hawaii, was born with microcephaly, the first case in the United States of brain damage linked to the virus. The baby and mother tested positive for a past Zika virus infection. The mother, who had probably acquired the virus while traveling in Brazil in May 2015 during the early stages of her pregnancy, had reported her bout of Zika. She recovered before relocating to Hawaii. Her pregnancy had progressed normally, and the baby's condition was not known until birth.

In March 2016, first solid evidence was reported on how the virus affects the development of the brain. It appears to preferentially kill developing brain cells.

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