RI Mosquito Report: State Announces Summer’s 5th Finding of West Nile Virus, Cautions Public to Prevent Mosquito Bites

Published on Friday, September 01, 2023

PROVIDENCE, RI – The Rhode Island Department of Environmental Management (DEM) and Rhode Island Department of Health (RIDOH) today announce the fifth detection of West Nile Virus (WNV) in a mosquito sample collected in the state this summer. The additional mosquito sample testing positive for WNV was collected in Cranston on Aug. 21. As announced earlier this week, the first detection of Eastern Equine Encephalitis virus (EEE) in Rhode Island in 2023 came from a mosquito sample collected in Glocester and the state’s fourth WNV detection came from a mosquito sample collected in Barrington. Overall, DEM collected 195 samples of mosquitoes from 25 traps set statewide on Aug. 21. All other samples tested negative for WNV and EEE.



To date, the Commonwealth of Massachusetts has announced 96 WNV findings, and the State of Connecticut reports 67 WNV findings. WNV and EEE findings in mosquitoes are expected because mosquito-borne diseases become more prevalent in Southern New England as the season progresses. To date, Massachusetts has confirmed two humans cases of WNV and Connecticut has confirmed one human case of WNV.

Although extremely rare in humans, EEE is very serious and has a much higher human mortality rate than WNV. Approximately 30% of people with EEE die and many survivors have ongoing neurological problems. Unlike WNV, which is prevalent in Rhode Island every year, EEE risk is variable, changing from year to year. With continued trapping and testing, DEM and RIDOH will be able to assess the EEE risk level this mosquito season. Neither Massachusetts nor Connecticut has reported any findings of EEE in mosquitoes, humans, or animals. For more information on EEE and ways to prevent it, please visit www.health.ri.gov/eee.

WNV is the leading cause of mosquito-borne disease in the continental United States and is much more prevalent than EEE. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick. About one in five people who are infected develop a fever and other symptoms. About one out of 150 infected people develop a serious, sometimes fatal, illness. For more information on WNV and ways to prevent it, please visit www.health.ri.gov/wnv.  



DEM and RIDOH advise Rhode Islanders to reduce their exposure to mosquitoes until the first hard frost. (A hard frost is when the air and the ground freeze below 32°F for three hours or below 28°F for two hours.) Personal protection is the first line of defense against mosquitoes that may carry WNV, EEE, or other diseases – and the most effective way to avoid infection. The following precautions are advised.

Protect yourself

  • Put screens on windows and doors. Fix screens that are loose or have holes.
  • At sunrise and sundown (when mosquitoes that carry EEE are most active), consider rescheduling outdoor activities that occur during evening or early morning. If you must be outside, wear long-sleeved shirts and long pants and use bug spray.
  • Use EPA-approved bug spray with one of the following active ingredients: DEET (20-30% strength), picaridin, IR3535, and oil of lemon eucalyptus or paramenthane. Always read the label and follow all directions and precautions.
  • Do not use bug spray with DEET on infants under two months of age. Check the product label to find the concentration of DEET in a product. The American Academy of Pediatrics recommends that repellents should contain no more than 30% DEET when used on children. Children should be careful not to rub their eyes after bug spray has been applied on their skin. Wash children’s’ hands with soap and water to remove any bug spray when they return indoors.
  • Put mosquito netting over playpens and baby carriages.

Remove mosquito breeding grounds

  • Remove items around your house and yard that collect water. Just one cup of water can produce hundreds of mosquitoes; an unused tire containing water can produce thousands of mosquitoes.
  • Clean your gutters and downspouts so that they can drain properly.
  • Remove any water from unused swimming pools, wading pools, boats, planters, trash and recycling bins, tires, and anything else that collects water, and cover them.
  • Remove or treat any shallow water that can accumulate on top of a pool cover. Larvicide treatments, such as Mosquito Dunks can be applied to kill immature mosquitoes. This environmentally friendly product is available at many hardware and garden stores and online.
  • Clean and change water in birdbaths at least once a week.

Best practices for horse owners

Horses are particularly susceptible to WNV and EEE. Horse owners are advised to vaccinate their animals early in the season and practice the following:

  • Remove or cover areas where standing water can collect.
  • Avoid putting animals outside at dawn, dusk, or during the night when mosquitoes are most active.
  • Insect-proof facilities where possible and use approved repellents frequently.
  • Monitor animals for symptoms of fever and/or neurological signs (such as stumbling, moodiness, loss of appetite) and report all suspicious cases to a veterinarian immediately. If you are unsure if your horse is properly vaccinated, you should consult with your veterinarian.

Visit health.ri.gov/mosquito for additional mosquito prevention tips, videos, and local data. Mosquitoes are trapped weekly by DEM and tested at the RIDOH State Health Laboratories. DEM issues advisories on test results from June through September, with additional reports as necessary. Typically, positive test results trigger additional trapping to assess risk. 

For more information on DEM programs and initiatives, visit www.dem.ri.gov. Follow DEM on Facebook, Twitter (@RhodeIslandDEM), or Instagram (@rhodeisland.dem) for timely updates.