The US may have just joined the other 67 countries and territories worldwide where mosquitoes are spreading the Zika virus, Popular Science reports. Up until now, all 1,600 Zika cases in the US were people who either traveled elsewhere to contract it or had sex with someone who did. But on Wednesday, the Florida health department announced four cases in Florida in which officials have ruled out both travel and sex. That means it's possible mosquitoes in Miami-Dade and Broward counties are spreading the virus.
Officials are surveying people within a 150-yard radius of the four cases, Reuters reports. That's the distance Zika-spreading mosquitoes are able to fly. So far, officials have interviewed about 200 people and asked for urine samples. They're also testing local mosquitoes. On Thursday, the FDA asked both Miami-Dade and Broward counties to stop all blood donations as a precaution, according to NPR. It's recommending neighboring counties do the same. (Read more Zika virus stories.)