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Thursday, September 1, 2016

No West Nile or EEE in latest mosquito samples

But DEM found some of the mosquito species that carry Zika

Image result for zika mosquitoThe Rhode Island Department of Environmental Management (DEM) today announced 172 mosquito samples from 32 traps set on Monday, August 15, 2016 have tested negative for both West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE).

Given concerns about the Zika virus, Rhode Island – like many states in the region – has increased surveillance for the Aedes albopictus mosquito species, which can transmit the virus. Six Aedes albopictus mosquitoes have been trapped in Barrington between August 15 and 22.

These six mosquitoes represent a tiny fraction of the overall 14,099 mosquitoes trapped in Rhode Island since June 1, 2016.

Due to this increased surveillance, additional trappings of individual Aedes albopictus are possible; however because Rhode Island winters have thus far been cold enough to kill most eggs of this species, mosquito experts don't expect the species' population to grow large enough to effectively spread the disease locally.

The primary mosquito species transmitting Zika virus is Aedes aegypti – which has never been found in Rhode Island and is limited to tropical and sub-tropical regions. 

All confirmed human cases of Zika in Rhode Island have been associated with travel out of state to areas with active Zika virus transmission. For more information on Zika and related travel safety tips, visit

The Rhode Island Department of Health advises that 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. Throughout the summer season, the public is encouraged to:

• Eliminate mosquito breeding grounds from yards by removing anything that holds standing water, such as old tires, buckets, junk and debris. Just one cup of standing water can produce hundreds of mosquitoes. Car and truck tires are especially of concern, as mosquito larvae are often found in tire piles. Be sure to continually empty any water accumulating in tires around your property.

• Clean gutters so they drain correctly.

• Make sure swimming pools are treated with chlorine, pumps are running properly, and any water that collects on pool covers is removed.

• Avoid mosquito bites by using screens on windows and doors, covering up at dawn and dusk, and putting mosquito netting over playpens and baby carriages when they are outside. Use mosquito repellent with at least 20 percent DEET but no more than 30 percent. Do not use repellent on infants.

To date, there has been one confirmed local finding of WNV in a mosquito sample and one confirmed finding of EEE in a mosquito sample in Rhode Island. WNV has also been detected in mosquito samples trapped in Massachusetts and Connecticut. EEE has also been confirmed in mosquito samples trapped in Massachusetts.

Mosquitoes are trapped weekly by DEM and tested at the State Health Laboratories at the Rhode Island Department of Health. DEM issues weekly advisories on test results from late June through September, with additional reports as necessary.

Test results are pending for the 33 traps set on August 22 and 24 and will be included in next week's announcement. Typically positive mosquito test results will trigger additional trapping to assess risk. As temperatures cool, mosquito populations will die out and testing will be suspended.

Visit for additional mosquito prevention tips and for local data. For more information about DEM divisions and programs, visit Follow us on Twitter (@RhodeIslandDEM) and/or Facebook at for timely updates.