WHO | WHO Director-General briefs Executive Board on Zika situation

The Zika virus was first isolated in 1947 from a monkey in the Zika forest of Uganda. Its historical home has been in a narrow equatorial belt stretching across Africa and into equatorial Asia.

For decades, the disease, transmitted by the Aedes genus of mosquito, slumbered, affecting mainly monkeys. In humans, Zika occasionally caused a mild disease of low concern.

In 2007, Zika expanded its geographical range to cause the first documented outbreak in the Pacific islands, in the Federated States of Micronesia. From 2013-2014, 4 additional Pacific island nations documented large Zika outbreaks.

In French Polynesia, the Zika outbreak was associated with neurological complications at a time when the virus was co-circulating with dengue. That was a unique feature, but difficult to interpret.

The situation today is dramatically different. Last year, the virus was detected in the Americas, where it is now spreading explosively. As of today, cases have been reported in 23 countries and territories in the region.

The level of alarm is extremely high.