WHO declares Zika a global emergency.

The World Health Organization declared the Zika virus and its suspected link to birth defects an international public health emergency, a rare move that signals the seriousness of the outbreak and gives countries new tools to fight it. An outbreak of the Zika virus, which is transmitted by mosquitoes, was detected in Brazil in May and has since moved into more than 20 countries in Latin America, including two new ones announced: Costa Rica and Jamaica.

Zika virus is related to dengue, yellow fever, Japanese encephalitis, and West Nile viruses. The illness it causes is similar to a mild form of dengue fever, is treated by rest, and cannot yet be prevented by drugs or vaccines. There is a possible link between Zika fever and microcephaly in newborn babies by mother-to-child transmission, as well as a stronger one with neurologic conditions in infected adults, including cases of the Guillain–Barré syndrome.