As of Oct. 19, 4,016 people in the United States have contracted Zika, and 899 of them are pregnant women, according to the CDC.
Of the 4,016 cases in the U.S., 137 were acquired from mosquitoes in Florida. The majority of the other cases are travel-associated, but 32 are classified as sexually transmitted.
Zika virus infection has been linked with birth defects such as microcephaly when it is contracted by a pregnant woman. As of Oct. 13, 23 infants in the U.S. have been born with Zika-related birth defects, and five pregnancies with Zika-related birth defects have been lost.
Not only can Zika virus be spread by mosquitoes and sexual intercourse, it can also spread via blood transfusions. The Food and Drug Administration recently confirmed a few units of donated blood in Florida tested positive for the virus. However, those donations did not make it into the blood supply.