Key takeaways
- About 80% of people infected with West Nile virus never feel sick; fewer than 1% develop a serious brain or spinal cord infection (CDC).
- In Florida the virus is carried mainly by two night-biting mosquitoes, the southern house mosquito and Culex nigripalpus.
- People 65 and older are three times as likely to develop neurologic illness, and there is no vaccine or antiviral medicine for people.
- Florida tracks the virus in sentinel chickens; by mid-October 2026, 359 had tested positive statewide, including flocks in Palm Beach County.
- Seek medical care right away for high fever, neck stiffness, muscle weakness, confusion or tremors after mosquito bites.
In this article
West Nile virus is spread mainly by Culex mosquitoes that bite at night, and most people who catch it never feel sick. About 1 in 5 develop a fever-type illness, and fewer than 1% develop a serious infection of the brain or spinal cord, according to the CDC. There is no vaccine for people and no medicine that treats the virus itself, so avoiding bites is the protection that counts.
West Nile has circulated in Florida since it was first identified in the state in 2001, according to UF/IFAS. Human cases are uncommon in most years, but state surveillance keeps finding the virus in birds and sentinel chickens, including in Palm Beach County in 2026. This guide explains how West Nile reaches people in South Florida, which symptoms to watch for, who is most at risk and how to cut your exposure at home.
How West Nile Virus Spreads
West Nile is a bird virus first. The CDC explains that it circulates mainly between birds and Culex mosquitoes: a mosquito picks up the virus by biting an infected bird and can later pass it to people, horses and other mammals. In Florida, UF/IFAS lists mourning doves, cardinals and Florida scrub jays among the birds that can become infected.
People and horses are dead-end hosts. They do not build up enough virus in their blood to infect the next mosquito, so a sick neighbor cannot “give” the virus to your local mosquitoes the way a dengue patient can. The risk to you depends on how much virus is moving between birds and mosquitoes in your area.
West Nile does not spread through coughing, sneezing, touching or handling live animals. Rare cases have been linked to blood transfusions, organ transplants and transmission from mother to baby during pregnancy, delivery or breastfeeding.
The Florida Mosquitoes That Carry It
Two Culex mosquitoes do most of the work in Florida, according to UF/IFAS:
- The southern house mosquito (Culex quinquefasciatus), Florida’s common house mosquito, lives mostly in urban areas. UF/IFAS says it prefers birds but also bites people and other mammals, feeds throughout the night and breeds in nutrient-rich standing water: birdbaths, old tires, storm-water catch basins and wastewater areas. Each female lays floating rafts of 100 or more eggs that hatch in about a day.
- Culex nigripalpus feeds mostly on birds in winter and spring, then switches to mammals in summer and fall. That shift is why UF/IFAS says the risk to people and horses rises in late summer and early fall.
This is the main difference from dengue, Zika and chikungunya, which are spread by daytime-biting Aedes mosquitoes. Our article on why Aedes mosquitoes are different from regular backyard mosquitoes compares the two groups in detail.
West Nile Virus in South Florida: What Surveillance Shows
Florida tracks West Nile through human cases, infected horses, mosquito samples and sentinel chickens, small flocks whose blood is tested for antibodies. A positive chicken means the virus is circulating among birds and mosquitoes nearby, often before anyone gets sick.
According to the Florida Department of Health surveillance report for October 11-17, 2026:
- Florida had 5 symptomatic human cases acquired in the state in 2026, all in North Florida counties (Alachua, Duval, Holmes and Walton), plus 2 infected blood donors without symptoms.
- 359 sentinel chickens had tested positive statewide, including flocks in Palm Beach, St. Lucie and Indian River counties on the southeast coast.
- Three horses were infected with West Nile in 2026.
- Miami-Dade was under a mosquito-borne illness alert, and Broward and Palm Beach under advisories. These warnings cover mosquito-borne illness in general, not West Nile alone.
The takeaway for South Florida: human West Nile cases are uncommon here, but the virus is present in the bird-mosquito cycle, and the night-biting mosquitoes that carry it breed in every neighborhood.
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West Nile Virus Symptoms
Symptoms usually start 2 to 6 days after the infected bite, but they can appear anywhere from 2 to 14 days later, and later still in people with weakened immune systems, according to the CDC.
Source: CDC, Symptoms of West Nile
| Form of illness | Typical symptoms | What to do |
|---|---|---|
| No symptoms (about 80%) | None | Nothing; most people never know they were infected |
| Febrile illness (about 20%) | Fever, headache, body aches, joint pain, vomiting, diarrhea or rash; fatigue that can last weeks or months | Call your doctor and mention mosquito bites |
| Severe neurologic illness (under 1%) | High fever, headache, neck stiffness, stupor, disorientation, tremors, convulsions, muscle weakness, vision loss, numbness, paralysis or coma | Seek medical care immediately |
The severe form, encephalitis or meningitis, affects the brain or the tissues around it and the spinal cord. The CDC reports that about 10% of people who develop it die, and survivors can need weeks or months to recover, sometimes with permanent effects.
Who Is Most at Risk of Severe West Nile Illness?
Anyone bitten by an infected mosquito can get West Nile, but some people are much more likely to become seriously ill. The CDC lists:
- Age. Risk rises with age; people 65 and older are three times as likely to develop neurologic illness as younger people.
- Chronic conditions such as cancer, diabetes, high blood pressure and kidney disease.
- A weakened immune system, including people taking medicines for cancer, autoimmune or inflammatory conditions, or to prevent transplant rejection.
Exposure matters too. Because the carriers bite at night, the people bitten most are those who spend evenings outdoors: on a patio, walking the dog after dark, fishing, working night shifts outdoors or sleeping in rooms with torn screens. For older adults, night-time bite prevention is the single most useful habit.
Horses are also vulnerable. UF/IFAS reports that about 10% of infected horses develop neurologic illness and recommends vaccinating horses with annual boosters.
How to Protect Yourself From West Nile Virus
The CDC is clear that no licensed vaccine or medicine prevents West Nile in people, so prevention means fewer bites and fewer mosquitoes. Against West Nile, focus on the hours from dusk to dawn, when the mosquitoes that spread it are most active.
Cover Up at Night
- Use an EPA-registered repellent whenever you are outside in the evening or at night, and follow the label.
- Wear long sleeves and long pants in loose fabric; bites go through tight clothing more easily.
- Keep window and door screens in good repair, or keep windows closed and use air conditioning.
- Limit outdoor time from dusk to dawn when you can, especially for older family members.
Drain the Water Culex Mosquitoes Use
Culex mosquitoes like water rich in organic matter, the kind that sits for days and turns dark or green. Around a South Florida home, check:
- Birdbaths and pet water bowls: empty and scrub them often
- Old tires, buckets, drums and broken appliances
- Unused or poorly maintained pools, hot tubs and pool covers
- Storm drains and catch basins near your property (report problems to your county)
- Clogged gutters and anything holding rain or sprinkler water
- Ponds, fountains and other permanent water you want to keep: the CDC suggests mosquito dunks or other larvicides, used according to the label
Our guide to 10 hidden spots where mosquitoes breed around your home walks through the less obvious places.
How Professional Mosquito Control Helps
Personal protection keeps mosquitoes off you; mosquito control reduces how many are around to bite in the first place. County mosquito control programs survey and treat across whole areas. In Miami-Dade and Broward you can call 311 to request a county inspection.
On your own property, Toro’s mosquito control service starts with a free inspection to find where mosquitoes breed and rest, from birdbaths and fountains to gutters, pool covers and shady areas. Technicians then treat breeding sites with larvicide granules and growth regulators and apply a barrier treatment made with plant oils to the vegetation where adults rest. You can book a one-time treatment before an event or a 3-month plan of 4 treatments, one every 3 weeks. Toro has protected South Florida homes and businesses since 1969, and its 110% Satisfaction Guarantee is simple: “If the bugs come back, so will TORO at no additional cost to you.”
To compare West Nile with the other infections mosquitoes carry here, read mosquito-borne diseases beyond dengue: Zika, West Nile and chikungunya, and browse our mosquito pest library to identify the species around your home.
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305-594-4767Frequently Asked Questions
Is West Nile virus contagious from person to person?
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Sources
- Symptoms of West Nile, Centers for Disease Control and Prevention
- West Nile: Causes and How It Spreads, Centers for Disease Control and Prevention
- West Nile virus, UF/IFAS EDIS
- Southern House Mosquito Culex quinquefasciatus Say, UF/IFAS Featured Creatures
- Florida Arbovirus Surveillance Week 41: October 11-17, 2026, Florida Department of Health
- Preventing West Nile, Centers for Disease Control and Prevention
Educational content. This article is for general information about pests in South Florida and is not medical, legal or professional advice. If you have a bite, sting or allergic reaction, contact your doctor; in an emergency, call 911. Pest problems vary from home to home, so a licensed professional should inspect before treatment. When using any pesticide, always read and follow the product label.
