New York State Department of Health Reminds New Yorkers to Protect Themselves Against Eastern Equine Encephalitis Virus and Other Mosquito-Borne Diseases

Confirmed Cases of EEE in Horses in Franklin and St. Lawrence Counties

Confirmed EEE in Onondaga County Mosquito Pools

ALBANY, N.Y. (August 22, 2023) - The New York State Department of Health is advising New Yorkers visiting or living in Central and Northern New York to take personal protective measures to avoid mosquito bites, after confirming the presence of eastern equine encephalitis (EEE) virus in horses in St. Lawrence and Franklin Counties, and in mosquitoes in some areas of Onondaga County. There are currently no human cases.

"Although human cases are rare, the State Health Department takes eastern equine encephalitis virus seriously, which can have a case fatality rate of 30 percent. There is no specific treatment for eastern equine encephalitis," said State Health Commissioner Dr. James McDonald. "We encourage people living in or visiting these counties to take proactive measures such as wearing long sleeves and pants during dawn and dusk, making sure there is no standing water nearby and using repellents to avoid mosquito bites. The State Health Department will continue to work with local health departments to help protect the health and safety of their residents."

Two cases of EEE have been confirmed in horses in St. Lawrence County, one case in a horse in Franklin County, and positive mosquito pools have been identified in Onondaga County. Additionally, Oswego County is continuing to perform mosquito surveillance activities, even though there are currently no EEE human cases or mosquitoes in the county. The Department of Health and the New York State Department of Agriculture and Markets sent a letter to veterinarians statewide to encourage surveillance for EEE in horses and other mammals.

EEE is a rare, but extremely serious viral disease spread by 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 greatest risk of acquiring the virus. While most people bitten by an infected mosquito will not develop any symptoms, severe cases 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 1971 there have been 11 confirmed human cases in New York State, the most recent (3) being in 2015.

There is no commercially available human vaccine for EEE, so the best way to protect yourself is to keep mosquitoes from biting you. Repellents provide protection against mosquito and tick bites. The federal Centers for Disease Control and Prevention (CDC) recommend choosing a repellent that contains an active effective ingredient such as DEET, IR3535, or oil of lemon eucalyptus for use on skin. Clothing and gear, such as boots, pants, socks and tents, can be treated with products containing permethrin. (Permethrin should not be used on skin.) Treated clothing or gear remains protective through several washings. Pre-treated clothing is also available and remains protective after multiple washings. For all repellents, it is important to follow the label directions and avoid contact with the eyes, nose or mouth. If you are also using sunscreen, apply sunscreen first and insect repellent second.

Reducing standing water around your property can also help to reduce mosquito populations that may spread disease.

New York State Agriculture Commissioner Richard A. Ball said, "Taking simple, proactive, preventive steps to protect yourself and your animals can be extremely effective in reducing the chance of getting ill from mosquito-borne diseases. If you're a horse owner and your horse is in need of a vaccination, I encourage you to make an appointment with your veterinarian as soon as possible."

Franklin County Public Health Director Kathleen Farrell Stack said, "A critical component of Franklin County mosquito surveillance is the rapid detection of and timely reporting of viral encephalitis and viral meningitis by medical providers for any patient with signs and symptoms consistent with these ailments. Mosquito bite prevention messages combined with surveillance and reporting aim to minimize mosquito borne virus infections throughout Franklin County."

Onondaga County Health Commissioner Dr. Kathryn Anderson said, "EEE is one of a number of viruses that can be spread by the bite of an infected mosquito. While mosquito counts in Central New York have been low throughout this season, it is always important to protect yourself and your family from mosquito bites."

St. Lawrence County Public Health Director Jolene Munger said, "Mosquitos are active until the first heavy frost and residents should continue to take measures to prevent mosquito bites. With the increase in rain fall this year, ensure your property is clear of standing water. If you own horses, talk to your veterinarian about vaccination and boosters for EEE."

Oswego County Public Health Director Vera Dunsmoor said, "Our mosquito surveillance program indicates their populations are at seasonal levels for this time of year. Still, we caution people to stay vigilant and protect themselves from mosquito bites as they can transmit harmful viruses such as eastern equine encephalitis virus and West Nile virus. While the chance of a person becoming infected with these viruses is small, they can cause serious illness or death. Following the personal protection guidance and limiting exposure to mosquitoes is the key to prevention."

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 will also be available on the Department's website and social media platforms to provide further public education emphasizing personal protection. For further information throughout mosquito season, a weekly mosquito-borne disease activity report published by the Department 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 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 23 - September 4.

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 for mosquitoes. Staff use the data to identify areas of disease risk and track trends in infections by geographic area and guide local decision-making and technical assistance regarding local mosquito control measures.
  • 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 and samples can be tested at the DOH Wadsworth Laboratory.
  • Animal surveillance: The Department, in conjunction with the Department of Agriculture and Markets and local health departments, maintain 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 insect repellent recommended for use on exposed skin.
  • 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.
  • Clean vegetation and debris from the edges of ponds.
  • Larvicide can be used according to label directions on areas where water collects and cannot be removed or drained - see guidance here.

For more information on eastern equine encephalitis virus visit: