The Rhode Island Department of Health (RIDOH) is announcing Rhode Island's first probable human case of West Nile Virus (WNV) in 2025. A person in their 60s from Providence County has tested positive for WNV and confirmatory testing will be conducted by the Centers for Disease Control and Prevention (CDC). The person's onset of symptoms began in early September and they remain hospitalized.
The most recent mosquito samples tested by the Rhode Island State Health Laboratories (RISHL) confirmed no mosquitoes samples statewide collected on September 15 have tested positive for WNV, Eastern Equine Encephalitis (EEE) virus, or Jamestown Canyon Virus. There have been no animal cases of mosquito-borne disease in Rhode Island this year, but 13 mosquito samples have been confirmed with WNV so far this season. Check RIDOH's arboviral surveillance data webpage for weekly test results. Rhode Island's risk level for WNV remains high statewide.
WNV is the leading cause of mosquito-borne disease in the continental United States and is much more prevalent than EEE virus. 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 about WNV, please visit health.ri.gov/wnv.
Although extremely rare in humans, EEE virus is very serious and has a much higher human mortality rate than WNV. Approximately 30% of people with EEE virus die, and many survivors have ongoing neurological problems. Unlike WNV, which is prevalent in Rhode Island every year, EEE virus risk is variable, changing from year to year. With continued trapping and testing, DEM and RIDOH will be able to assess the EEE virus risk level this mosquito season. For more information on EEE virus and ways to prevent it, please visit health.ri.gov/eee.
Mosquito Control:
Residents can help control mosquitoes by removing backyard mosquito breeding grounds. The Asian Tiger Mosquito has become prevalent in Rhode Island urban environments, and it is expected to be common again this season. It is notable as a daytime biter encountered in shaded backyards. It has a striking black and white pattern evident to the naked eye. It develops from eggs laid in artificial containers, so residents are urged to remove standing water from containers such as buckets, pots, wheelbarrows, boats, and pools. Clogged rain gutters and puddles formed on tarps also can support the larvae of this species. The Asian tiger mosquito is known to transmit several diseases, including WNV.
Rhode Islanders should take the following measures to protect themselves from mosquito bites and to help minimize mosquito breeding:
Protect yourself! • Put screens on windows and doors. Fix screens that are loose or have holes. • Consider rescheduling outdoor activities that occur during the evening or early morning at sunrise and sundown (when mosquitoes carrying the EEE virus are most active). If you must be outside, wear long-sleeved shirts and 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 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.
Visit health.ri.gov/mosquito for additional mosquito prevention tips, videos, and local data. DEM traps mosquitoes weekly and tests them at the RIDOH State Health Laboratories. Typically, positive test results trigger additional trapping to assess risk.