Florida’s State Surgeon General, Dr. John Armstrong, released the latest data on imported cases of Zika viral illness in his state on March 7. At this time, the state has confirmed 50 patients who have had or are experiencing the mosquito borne illness, from 11 counties. Four of those are pregnant women.
Miami-Dade County has 24 of the Zika illnesses. None of the other counties are reporting more than 7. The Department of Health is not reporting the counties of residence for the four pregnant women.
All 50 Zika cases were contracted outside the United States and imported. There have not been any locally contracted cases of Zika viral illness at this time. Arbovirus surveillance in Florida for the week ending March 5, 2016, reports that the top three countries of origin for the imported Zika cases are Colombia with 13, Venezuela with ten and Haiti with nine.
The Zika virus is spread by biting female mosquitoes of two species, Aedes aegypti and Aedes albopictus. Ae. aegypti is also known as the yellow fever mosquito. It is an aggressive daytime biter, and will enter and live indoors if the conditions are right. It feeds nearly exclusively on humans. Ae. albopictus is equally aggressive but will feed on animals other than humans.
The Examiner surveyed a number of mosquito control agencies in Florida about the emergence of both Aedes species in their locality.
Beth Ranson, from the Florida Keys Mosquito Control District, states “We have Aedes aegypti year-round in the Florida Keys and have Aedes albopictus is a few isolated areas.”
Gary Goode works with the Mosquito Control Division of the Palm Beach County Dept. of Environmental Resources Management. He told the Examiner “Here in South Florida our mosquitoes really don’t experience an “off-season”. They are active year around, and we will see both of these species whenever there is enough rain. That’s not much rain at all when they can breed in as little as a thimble of water. Even during dry spells, there usually is enough water to keep them going, since lawn sprinklers will do the trick just as well as rain can.”
Glen-Paul Edson, from Pinellas County Mosquito Control, reported “Unlike the north where it is cold here in South Florida it is warm enough to have year round mosquitoes. And both species mentioned, as well as the other 34 species we have in Pinellas county are active and breeding year round.”
Jim McNelly, Director of Volusia County Mosquito Control, noted that his county is far enough north that Aedes mosquitoes do not appear year round. “Mid to late April, very low population numbers. Population increases through May. Mid to latter part of May through early Oct is what we consider to be our season for these 2 mosqs.”
Farther north, on Florida’s panhandle, Scott R. Henson from Okaloosa County Public Works, told the Examiner that “According to 2015 surveillance data, Ae. albopictus emerged around April 2 and remained under 1% of total trapped until the end of May. The average high percentage of mosquito’s trapped hovered around 10% throughout the rest of the summer. There were no Ae. aegypti found in any trapping we did last year.”
Zika continues to spread in the Americas. The mosquito vectors for the illness are alive and flying in South Florida at this time. All of the confirmed cases to date were contracted out of the country but the potential for the disease to become locally acquired is very high.
As the number of imported cases climbs in the state, so do the number of undiscovered illnesses. The chances that local Aedes mosquitoes will be infected by biting an infected person also increases and, sooner or later, Zika will be locally acquired in Florida.