The mosquito-borne Zika virus, which first appeared in May 2015 and caused panic in Brazil among pregnant women, has since spread to 20 other countries and territories of the Americas and is likely to spread further, warned the World Health Organization (WHO) last week.
Nearly 3,000 babies in Brazil have been born with microcephaly, a birth defect that results in an abnormally small head and brain, and causes devastating brain damage. Although a link between the two has not been definitely established, the Brazilian government has taken the unprecedented step of advising women to avoid pregnancy until the crisis has been solved.
Zika virus, first identified in Uganda in 1947, is transmitted by the same type of mosquito that carries dengue fever, yellow fever, and chikungunya virus. A mosquito bites an infected person and then passes those viruses to other people it bites. Outbreaks outside of Africa began in 2007, when it spread to the South Pacific.
There are two main reasons for the virus' current rapid spread: (1) the population of the Americas had not previously been exposed to Zika and therefore lacks immunity, and (2) Aedes mosquitoes — the main vector for Zika transmission — are present in all the region's countries except Canada and continental Chile, said WHO.
The disease can cause fever, flu-like symptoms, rash, joint pain, and conjunctivitis, also called pinkeye. But most people will not know they have it. Only about 1 in 5 people with the virus will exhibit symptoms, the vast majority have no symptoms at all. The symptoms range in severity and can last from a few days to more than a week.
The virus rarely causes major complications, but in rare cases, Zika can cause partial or complete paralysis, most often temporary. Microcephaly, the malady now associated with Zika, results in some fetuses being stillborn and many dying early in age or having very severe lifelong cognitive problems.