Congress adjourned for summer recess on July 15 with no plan in place for battling Zika. Should Congressional members ignore Reid's request, they'll remain on break until September 6.

While sexual transmission as the cause of the new cases has not yet been ruled out, health officials are investigating and so far it appears that they could be due to a local outbreak rather than to other means of infection.

The report said that, despite 1,400 cases already reported within the continental United States, up till now nearly all were acquired via travel outside the country. Fifteen were sexually transmitted, and infection in a laboratory caused a sixteenth case. But these four so far appear to have been caused by direct infection rather than by other means.

The more people who return to the United States with the infection, the more the odds increase that the disease will end up spreading, since a local mosquito biting an infected person could then become infectious and transmit the disease through future bites.

That said, a wide outbreak in the continental United States is not expected, because populations are not as dense in the United States and there is much broader use of both screens and air conditioning than in the Caribbean and Latin America, where the disease has experienced greater spread.

Florida is considered a high-risk area for transmission of the disease, which is carried by Aedes aegypti mosquitoes. The state has been one of the few continental U.S. locations to see the spread of similar diseases, such as dengue and chikungunya. And there are already more than 380 reported cases of Zika in Florida, although they are travel related. Adults, except for high-risk individuals, usually only experience a mild illness, but 53 of those cases are pregnant women; Zika presents particular birth defect risks to the fetus.

Residents of the two counties who live near the newly reported cases are being tested for the presence of the virus, and officials are also trapping mosquitoes to test them as well — though they say in the report that, “depending on the number of mosquitoes, that could be like looking for a needle in a haystack.”