Zika Virus

For decades after its discovery, the Zika virus was considered no great threat to anyone. It had caused only occasional documented cases of disease apart from several outbreaks in remote Pacific islands, and even so was thought to produce only mild flu-like symptoms. Zika’s days of obscurity are over. After spreading rapidly through the Americas starting in 2015, mosquitoes carrying the virus had reached 84 countries and territories around the world by March 2017. It has caused a jump in the number of birth defects and is strongly suspected in an increase in cases of a rare neurological disorder.

The Zika virus, which is carried by the Aedes mosquito, produces symptoms such as rash, fever, joint pain and pinkeye in about 1 in 5 people infected. As it spread, Brazil recorded a 20-fold increase in the incidence of microcephaly, a rare condition in which an infant’s head is abnormally small. Subsequently, the condition, as well as birth defects including brain irregularities, vision problems and hearing loss, were connected to Zika infections in pregnant women. Of the 250 pregnant women in the U.S. with a confirmed Zika infection in 2016, 24 — or about 1 in 10 — had a fetus or baby with Zika-related defects, according to the U.S. Centers for Disease Control and Prevention. Both figures are rising. The World Health Organization reports that 31 countries or territories have registered microcephaly or related cases that may be linked to Zika. Twenty-three have reported either an increased incidence of Guillain-Barre syndrome, a sometimes deadly nerve disorder that can cause paralysis, or Zika infection among Guillain-Barre cases. A 2013 Zika outbreak in French Polynesia coincided with a spike in the syndrome, and researchers strongly suspect a link. There are no specific drugs to treat Zika and no vaccine to prevent it, though drugmakers and the U.S. government are working on both.