Resident of southern part of city of Sarasota infected with West Nile virus, health officials report

County’s Mosquito Management Services staff focusing treatments on that area and warning public to be cautious

Wade Brennan, manager of Sarasota County Mosquito Management Services, addresses members of the news media on Oct. 17. Image created from a county video.

A resident of the southern part of the city of Sarasota appears to have contracted West Nile virus locally in September, necessitating intensive treatments of the area where the person lives, the manager of Sarasota County’s Mosquito Management Services reported this week.

The confirmation of the case also prompted a county mosquito-borne illness advisory this week from Sarasota County staff.

In an email sent out to members of the news media the evening of Oct. 16, Jamie Carson, director of the county’s Communications Department, reported, “Staff surveyed and treated all the areas at risk, and increased adulticide and larvicide treatments by foot, truck, and planes. These missions have been conducted on a continuous basis where needed. Residents are encouraged to protect themselves from mosquito bites by draining and covering standing water on their property, wearing repellant, and wearing long-loose-fitting clothing.”

On Oct. 17, Wade Brennan, the manager of Mosquito Management, told reporters during a media briefing that he and his staff were informed in September that the infected person was under investigation in regard to how the individual acquired the illness. As a result, Brennan added, his staff “conducted a lot of surveillance” in the southern part of the city.

“So now our crews are going back into that area, now that this has been confirmed, and making sure those [treatment and surveillance] actions are still taking place and that we have control over that mosquito population.”

The infected city resident had traveled out of state prior to the infection, Brennan continued, but, based on the disease’s incubation period, health officials believe the individual acquired the illness in the city of Sarasota.

Nonetheless, in an Oct. 17 response via email to a Sarasota News Leader question, Brennan wrote, “The mosquito species that vector West Nile Virus travel greater distances, more than 2 miles potentially. Mosquito Management Services doesn’t know where this person was bitten by the infected mosquito [as] it could have been in Sarasota or out of State.”

In her Oct. 16 advisory, Carson included a copy of an email that Chuck Henry, director of the Florida Department of Health in Sarasota County (DOH-Sarasota), sent to the county commissioners at 5:36 p.m. the same day.

Henry wrote, “DOH is issuing a mosquito-borne illness advisory for Sarasota County due to a single confirmed human case of West Nile Virus. The case occurred in early September and has already been treated. Laboratory confirmation was just received and we anticipate that the case will appear in the Weekly Florida Arboviral Report this week Arboviral Report.”

The report Henry referenced is produced each week by the Florida Department of Health in Tallahassee. Indeed, the report for the period of Oct. 8 through Oct. 14 says, “One human case of WNV [West Nile virus] infection was reported this week in Sarasota County. No horses with WNV infection were reported this week. Twenty-four sentinel chickens tested positive for antibodies to WNV this week in Bay, Duval, Nassau, Orange, St. Johns, Volusia, and Walton counties. No mosquito pools tested positive for WNV this week. In 2023, positive samples from seven humans, two asymptomatic blood donors, 155 sentinel chickens, one pheasant, and two horses have been reported from 17 counties.”

This is the top of the Oct. 8-14 Arbovirus Report from the Florida Department of Health in Tallahassee.

As Brennan of Mosquito Management explained during the Oct. 17 media briefing, West Nile virus typically is transmitted by specific species of mosquitoes that have bitten birds carrying the virus. Sarasota County and other jurisdictions use “sentinel chickens” as a means of making routine checks on the presence West Nile Virus in the community, county staff has explained.

In response to another News Leader question, Brennan wrote in his Oct. 17 email, “The last positive sentinel chicken that Mosquito Management Services had was in February. Mosquito Management Services had only one positive chicken this year. Mosquito Management Services tested over a thousand mosquito collections throughout the year and none of them tested positive. The last human case of WNV we had was just prior to Hurricane Ian,” which struck the county in late September 2022.

Henry added in his email to the commissioners, “Surveillance indicates that there has not been an increase in mosquito-borne disease activity in sentinel chicken flocks or mosquito pools. Nonetheless, DOH-Sarasota reminds residents and visitors to avoid being bitten by mosquitoes and to take basic precautions to help limit exposure. DOH has posted a video on West Nile for Citizens to review on our webpage at

It is not common, Brennan said during the briefing, for the female mosquitoes that transmit West Nile virus to bite humans.

Brennan also noted that September and October are the peak months for West Nile virus risk in this area.

Symptoms of the illness and the carriers

This is a CDC graphic about West Nile virus. Image from the CDC website

Additionally, Brennan indicated that West Nile Virus is less of a concern than malaria, with which he and his staff contended earlier this year. Nonetheless, Brennan emphasized that West Nile Virus is serious, as it can have life-long effects.

The U.S. Centers for Disease Control and Prevention (CDC) says that most people who contract West Nile Virus “do not develop any symptoms.”

The agency adds, “About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness [fever] due to West Nile virus recover completely, but fatigue and weakness can last for weeks or months.”
Then the CDC points out, “About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

“Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.

“Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk for severe illness if they are infected (1 in 50 people). People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.

“Recovery from severe illness might take several weeks or months. “Some effects to the central nervous system might be permanent.

“About 1 out of 10 people who develop severe illness affecting the central nervous system die,” the CDC adds.

“Mosquitoes of the genus Culex are generally considered the principal vectors of WNV, in particular Cx. Pipiens,” the World Health Organization says.

However, Brennan identified the two species that he and his staff are targeting as Culex quinquefasciatus, known as the Southern house mosquito, which can be found in the Southeastern United States, and Culex nigripalpus. The National Institutes of Health points out that the latter species is “also an important vector” for West Nile virus in the Southeastern United States.

The cooler, drier weather this week “is greatly helping our situation,” Brennan said during the media briefing, especially the “sudden reduction of rain.”

Hurricane Idalia’s passage through the Gulf of Mexico produced rain in Sarasota County, and that was followed by cold fronts that brought precipitation; the rain boosted the mosquito population, he explained.

The Culex mosquitoes, he added, “really thrive in … wet, hot, humid conditions …”

Nonetheless, Brennan noted, “This has been an extremely low activity year” for West Nile Virus, “so that’s very fortunate.” That is the primary reason, he indicated, that he and his staff do not believe this situation is as big a threat as malaria was during the late spring and summer.

For more information on Mosquito Management Services, mosquito-borne illness, and spray missions, or to submit a service request, Carson of Communications wrote in her advisory, persons may call 311 or visit