New York State Department of Health Reminds New Yorkers To Take Precautions Against West Nile Virus

First Human West Nile Cases Reported This Year in New York State

New Yorkers Encouraged to Take Precautions to Prevent Mosquito Bites

Risk of Severe Arboviral Illness in Individuals Taking B-Cell Depleting/Modulating Therapies

ALBANY, N.Y. (August 26, 2026) - The New York State Department of Health reminds New Yorkers it is important to take precautions to prevent mosquito bites and protect against diseases like West Nile virus (WNV) and Eastern equine encephalitis (EEE). Working with local health departments, the Department tracks mosquito and mosquito-borne disease activity across the state and publishes weekly surveillance reports. Human cases of WNV have now been reported in Nassau, Onondaga, and Suffolk counties as well as in New York City.

"Mosquito bites are not only painful, annoying and itchy, they can carry serious illness, such as West Nile virus and Eastern equine encephalitis," New York State Health Commissioner Dr. James McDonald said. "When enjoying New York's great outdoors, prevent mosquito bites by using insect repellent or physical barriers. When opening windows in your home, be sure screens are in place and intact."

West Nile virus (WNV) is transmitted to humans and some animals through the bite of an infected mosquito. WNV was first identified in New York State in 1999. Over the last 10 years, 574 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. If illness develops, symptoms usually occur 2-14 days after the bite from an infected mosquito. People with mild cases of mosquito-borne disease may develop fever, headache, body aches, and occasionally a skin rash or swollen glands. People with severe illness from WNV may have a sudden onset of headache, high fever, neck stiffness, muscle weakness, altered mental status, or inflammation of the brain (encephalitis) and the membranes around the brain and spinal cord (meningitis).

There is no specific treatment available for WNV and antibiotics cannot treat the viral infection. Patients are treated for their symptoms and provided supportive therapy. Of the less than 1 in 150 people with severe WNV disease, death is very rare and almost all patients recover completely. In cases of severe disease, supportive therapy may include hospitalization, respiratory support, IV fluids and treatment of other infections that develop. People with mild symptoms of WNV usually recover completely.

Eastern equine encephalitis (EEE) is a rare but severe viral disease spread by infected mosquitoes that can affect people and horses. People of all ages are susceptible to infection, but people over 50 and younger than 15 are at a high risk of acquiring the virus. While most people bitten by an infected mosquito will not develop symptoms, severe cases may begin with the sudden onset of headache, high fever, chills and vomiting. The illness may then progress into disorientation, seizures, encephalitis and coma. Approximately a third of patients who develop EEE die, while many patients who survive EEE experience neurologic impairment. Since 2024, three cases of EEE were reported among NYS residents; two of the cases were fatal.

There is no commercially available human vaccine for EEE, and the best protection is to prevent mosquito bites.

While rare, other mosquito-borne viruses including Jamestown Canyon virus (JCV) and Cache Valley virus (CVV), can also cause severe neurological disease and are often associated with infection of immunocompromised individuals.

The Department has recently released a health advisory for healthcare providers concerning the risk of severe arboviral disease in patients on B-cell depleting or modulating medications, particularly anti-CD20 monoclonal antibodies, such as rituximab. Patients and their providers should be aware of this risk to help patients protect themselves against the bites of mosquitoes and ticks, which can increase patients' risk of arboviral disease.

Components of the State Health Department's mosquito plan include:

Mosquito Education and Outreach

The Department of Health has issued a seasonal mosquito-borne disease health advisory to all local health departments and health care providers, on symptoms and diagnostic procedures for West Nile virus (WNV) and EEE. This information is also available on the Department's website.

The Department's social media platforms also provide public education emphasizing personal protection. For further information throughout mosquito season, the Department's weekly mosquito-borne disease activity reports can be found here.

In order to protect pets and animals that may also contract or carry these diseases, the Department also provides information to veterinary medical practitioners on the appropriate procedures for vaccinating against and diagnosing mosquito-borne illness.

In addition, the Department will provide educational materials about mosquito-borne diseases at The Great New York State Fair which runs from August 26 - September 7.

Mosquito Surveillance and Assistance

  • Mosquito surveillance: Working with various county health departments, starting in early summer, the Department coordinates the weekly collection and identification of mosquitoes from traps located in key habitats. Trapped mosquitoes are sent to the Wadsworth Center for pathogen testing. Staff use the data to identify areas of disease risk, track trends in infections by geographic area, and guide local decision-making and technical assistance regarding mosquito control measures. Further information about surveillance testing can be found here.
  • Human surveillance: Each summer, the Department sends alerts to increase healthcare providers' awareness of the symptoms of WNV and EEE. When providers suspect a mosquito-borne illness, the Department in cooperation with county health departments investigates these illnesses, and patient samples can be tested at the DOH Wadsworth Laboratory. Information about available tests and sample submission can be found here.
  • Animal surveillance: The Department, in conjunction with the Department of Agriculture and Markets and local health departments, maintains veterinary surveillance for encephalitis in horses. Horses are very sensitive to EEE and infection is often fatal. Suspected cases are tested at the Department's Wadsworth Laboratory to confirm infection. Vaccines are available to help protect horses from EEE and WNV. Horse owners should ensure their horses are up to date on vaccines against EEE/WNV and minimize exposure to infected mosquitoes by frequently changing water in troughs and buckets and eliminating other standing water sources.

Mosquito Prevention Tips

The Department recommends the following precautions to reduce risk of infection from mosquito-borne diseases:

  • Cover your skin as completely as possible while outside when mosquitoes are present and active. Wear long sleeves, pants and socks.
  • Use EPA-registered insect repellent recommended for use on exposed skin.
  • Wear permethrin-treated clothing and gear.
  • Always follow label directions before using any kind of repellent.
  • Reduce or eliminate all standing water in yards.
  • Remove discarded tires and turn over containers in which water can collect.
  • Make sure all windows and doors have screens and are free of rips, tears or holes.
  • Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
  • Drain water from pool covers.
  • Clear vegetation and debris from the edges of ponds.
  • Larvicide (Mosquito Dunks ®) can be used according to label directions on areas where water collects and cannot be removed or drained - see guidance here.