For the first time ever, an American has contracted the Zika virus while residing in the United States, according to the Centers for Disease Control. Until now, the 36 U.S. residents with confirmed cases of the virus had become infected while traveling abroad. Since the disease is typically spread through mosquito bites, health officials had expected most of the country to be spared any threat of domestic Zika infection until the end of the winter. But now a Dallas resident has contracted the virus via sexual intercourse, a local NBC affiliate reports.
“A person who recently traveled to an area with Zika virus transmission returned to the United States and developed Zika-like symptoms. The person later tested positive for Zika, along with their sexual partner, who had not traveled to the area,” the CDC said in a statement.
Epidemiologists believe that sexual transmission plays a far less significant role in spreading the virus than do mosquito bites. Nonetheless, officials are urging residents to exercise caution — if you’re going to have sex with someone who recently traveled to South America, Dallas County suggests that you use protection.
On Monday, the World Health Organization declared Zika a global emergency. The infection is native to Africa, but spread to the western hemisphere — where populations lack natural immunity to the virus — in 2015. The illness was first detected in Brazil last May, and has since spread to 21 countries in the Caribbean and the Americas.
Zika is thought to have contributed to a sudden spike in cases of babies born with abnormally small heads, a condition known as microcephaly. The WHO has set up a global-response unit to deal with the crisis. U.S. officials say that their mosquito-control programs are effective enough to prevent a major outbreak.
The newest case of Zika marks 37 confirmed cases in the U.S. including four pregnant women and five New Yorkers. There are still no known cases of mosquito-transmitted Zika virus in the U.S.