Nearly 200 cases of Zika infection have been reported in the United States, and there are fears the number will continue to grow.
Health officials released the numbers Thursday and pleaded for Congress to provide $1.9 billion to fight the virus in Latin America and help prevent it from spreading to the continental U.S.
Some of the money would go to Puerto Rico, where Zika is spreading locally and 159 cases have been reported.
Capitol Hill Republicans have deferred the request, insisting leftover funds from dealing with the Ebola crisis can be used. Health officials say new funding is needed.
So far, all of the cases in the U.S. can be traced to travel abroad in areas where the virus is spreading, mostly in Latin America. In a handful of cases, patients contracted the virus through sex with someone who was infected abroad.
Zika virus is mainly spread through mosquito bites, although sexual transmission can also occur. In most people, it causes only mild symptoms. But there's growing evidence linking it to a rare birth defect called microcephaly, where infants are born with small heads and often brain damage, and to a nerve condition that causes temporary paralysis.
The U.S. Centers for Disease Control and Prevention is recommending that pregnant women delay travel to areas where Zika is present. The government health agency is also advising that until more is known, pregnant women and their male sex partners who have lived in or traveled to an area where Zika virus is spreading should either use condoms during sex or abstain from sex throughout pregnancy.
Preventing mosquito bites can help reduce transmission of the Zika virus. The CDC recommends wearing long-sleeved pants and shirts, using EPA-approved insect repellents, staying indoors with air conditioning or screens on doors and windows, and removing standing water (in flower pots and buckets, for example) where mosquitoes breed.