New York State Health Department Issues Mosquito-Borne Disease Alert as West Nile Virus Detected in Three Counties
Key Insights
The New York State Department of Health (search) confirmed West Nile Virus (search) in mosquito pools across Nassau, Rockland, and Suffolk counties as of July 15, 2026.
Over the last decade, 569 human cases and 30 deaths from WNV have been reported statewide, though the majority of infections remain undiagnosed.
No specific antiviral treatment or commercially available human vaccine exists for WNV or Eastern Equine Encephalitis (search); supportive therapy remains the standard of care.
The New York State Department of Health (search) (NYSDOH) has confirmed the presence of West Nile Virus (search) (WNV) in mosquito pools in Nassau, Rockland, and Suffolk counties, prompting a statewide reminder for residents to take precautions against mosquito-borne diseases. The announcement, made on July 15, 2026, coincides with the Department's ongoing weekly mosquito-borne disease surveillance and reporting efforts conducted in partnership with local health departments.
"Mosquitoes are not our friends. Preventing mosquito bites stops the nuisance itching and can prevent rare and potentially serious illnesses," said New York State Health Commissioner Dr. James McDonald. "Prevention measures, such as insect repellant, removing standing water near your home and appropriate clothing are examples of common-sense strategies to prevent rare yet serious diseases such as West Nile virus (search) and Eastern Equine Encephalitis (search) virus."
West Nile Virus (search): Clinical Profile and Burden
West Nile virus (search), first identified in New York State in 1999, is transmitted to humans and some animals through the bite of an infected mosquito. Over the last 10 years, 569 human cases and 30 deaths from WNV have been reported statewide, yet the majority of infections remain undiagnosed. Most people infected with WNV do not develop any signs or symptoms. When illness does occur, symptoms typically manifest 2 to 14 days after the bite from an infected mosquito.
Mild cases may present with fever, headache, body aches, and occasionally a skin rash or swollen glands. Severe cases, which occur in less than 1 in 150 infected individuals, can involve sudden onset of headache, high fever, neck stiffness, muscle weakness, altered mental status, tremors, convulsions, paralysis, inflammation of the brain or the membranes of the brain and spinal cord, or coma. Despite the severity of these manifestations, death is very rare and almost all patients recover completely.
There is no specific treatment available for WNV, and antibiotics cannot treat the viral infection. Patients receive symptomatic treatment and supportive therapy. In severe cases, supportive therapy may include hospitalization, respiratory support, IV fluids, and treatment of secondary infections. People with mild symptoms usually recover completely.
Eastern Equine Encephalitis (search) and Other Arboviral Threats
Eastern equine encephalitis (search) (EEE) represents a rarer but more lethal mosquito-borne threat. While most people bitten by an infected mosquito will not develop symptoms, severe cases may begin with sudden onset of headache, high fever, chills, and vomiting, potentially progressing to disorientation, seizures, encephalitis, and coma. Approximately one-third of patients who develop EEE die, and many survivors experience lasting neurologic impairment. People over 50 and younger than 15 are at particularly high risk.
No commercially available human vaccine exists for EEE, making bite prevention the sole protective strategy. Other mosquito-borne viruses, including Jamestown Canyon virus (search) (JCV) and Cache Valley virus (search) (CVV), can also cause severe neurological disease and are often associated with infection of immunocompromised individuals.
Multi-Pronged Surveillance Strategy
The NYSDOH's mosquito plan encompasses education, outreach, and comprehensive surveillance across three domains. Mosquito surveillance involves weekly collection and identification of mosquitoes from traps located in key habitats, with data used to identify areas of disease risk, track geographic trends, and guide local mosquito control decisions.
Human surveillance includes seasonal health advisories to local health departments and healthcare providers regarding symptoms and diagnostic procedures for WNV and EEE. When providers suspect a mosquito-borne illness, the Department investigates in cooperation with county health departments, and samples can be tested at the DOH Wadsworth Laboratory.
Animal surveillance, conducted jointly with the Department of Agriculture and Markets, maintains veterinary monitoring for encephalitis in horses. Horses are highly sensitive to EEE, and infection is often fatal. Vaccines are available to protect horses from EEE and WNV, and horse owners are urged to keep vaccinations current.
Prevention Recommendations
The Department recommends several precautions to reduce infection risk: covering skin with long sleeves, pants, and socks when mosquitoes are active; using EPA-recommended insect repellent on exposed skin; wearing permethrin-treated clothing and gear; eliminating standing water in yards; removing discarded tires and containers that can collect water; ensuring windows and doors have intact screens; cleaning and chlorinating swimming pools, outdoor saunas, and hot tubs; draining water from pool covers; cleaning vegetation and debris from pond edges; and using larvicide according to label directions on areas where water cannot be removed or drained.
The Department will also provide educational materials about mosquito-borne diseases at The Great New York State Fair, running from August 26 through September 7, 2026.