Mike Stobbe - Associated Press

The alert comes a few days after a locally acquired case was identified in Hillsborough County. The virus remains less common in the continental U.S., but there have been three times more cases than at this point last year.

The study found military personnel stationed at Camp Lejeune from 1975 to 1985 had at least a 20% higher risk for a number of cancers. The list includes some types of leukemia and lymphoma and cancers of the lung, breast, throat, esophagus and thyroid.

It's not clear why infectious cases of syphilis rose 9% while gonorrhea dropped 9%, the CDC reports. Syphilis is less common than gonorrhea or chlamydia but considered more dangerous.