So far, no mosquitoes trapped by the Florida health department have tested positive for Zika, but officials say it's highly likely these four cases were transmitted via local mosquitoes. The department is going door-to-door notifying and testing residents in the affected area, and blood donations are on hold in the region until screening protocols can be established.

The Zika virus is particularly problematic for pregnant women, as the Centers for Disease Control and Prevention has confirmed it causes severe fetal brain defects such as microcephaly. Zika can be spread via infected mosquitoes or through sex with someone carrying the disease. In June, the CDC warned that certain breeds of mosquitoes in the US could spread Zika if they came in contact with an infected person. The organization laid out a five-step plan to contain active transmission sites in the US.

There are more than 1,300 travel-related cases of Zika across the continental US. Florida health officials have confirmed 331 cases of Zika not involving pregnant women and 55 cases involving pregnant women. The health department urges Floridians to drain standing water weekly and use mosquito repellent when outdoors. There's a Zika Virus Information Hotline set up in the state for anyone, local or visiting, who has questions about the disease. Reach the hotline at 1-855-622-6735.