TAMPA, Fla. (Reuters) – Florida Governor Rick Scott declared a public health emergency in four counties with travel-related cases of the Zika virus on Wednesday, and ordered state officials to increase mosquito control efforts in some of the most populous parts of the state.

“Although Florida’s current nine Zika cases were travel-related, we have to ensure Florida is prepared and stays ahead of the spread of the Zika virus in our state,” Scott said in a statement.

The counties are Miami-Dade in south Florida, Hillsborough in the Tampa Bay region, Lee County in southwest Florida and Santa Rosa County in the Florida Panhandle.

Scott directed the state’s surgeon general to declare the public health emergency, and for state officials to pay special attention to mosquito spraying in residential areas in those counties.

Florida is the third most populous state in the country.

The mosquito-borne virus, which is rapidly spreading in the Americas, has been linked to a spike in birth defects in thousands of babies in Brazil.

The World Health Organization declared a global health emergency on Feb. 1, citing a “strongly suspected” relationship between Zika infection in pregnancy and microcephaly, a condition marked by abnormally small head size that can cause permanent brain damage in newborns.

Scott noted in an executive order that the type of mosquito that transmits Zika is common in Florida, where a warm climate provides for a nearly year-round mosquito season. The virus, first identified in 1947 in Uganda, is spread by the Aedes aegypti mosquito.

(Reporting by Letitia Stein; Editing by Bernard Orr)