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Published on September 10, 2019

What you should know about EEE and West Nile

Mosquito Disease

It may be after Labor Day, but the mosquitoes that spread West Nile virus and deadly EEE (Eastern Equine Encephalitis) are still active on Cape Cod.

There is no vaccine or specific treatment for these two diseases, which can both be fatal, so prevention is the only way for people to protect themselves, said infectious disease specialist Ana Paula Oppenheimer, MD, of Infectious Disease Clinical Services at Hyannis and Falmouth Hospitals.

Dr. Oppenheimer’s clinic sees patients in whom mosquito- and tick-borne borne illnesses are suspected. Often they are older patients exhibiting confusion and fever and have been outside in an area where mosquitoes have tested positive for carrying EEE or West Nile, or which has ticks infected with Lyme disease, babesiosis or other illnesses. Severe cases are admitted to the hospital and a lumbar puncture needs be done to examine spinal fluid.

“We always ask about exposure and if and where patients have traveled,” Dr. Oppenheimer said. Time elapsed since onset of symptoms is also key to diagnosis.


On Cape Cod, mosquitoes carrying the EEE virus have been found in Falmouth, Bourne, Wellfleet and Truro, though no human cases have been reported here this year. However, as of September 6, seven cases have been confirmed elsewhere in the state, and eight infected horses have been reported, according to the state Department of Public Health. One death has been reported, a Fairhaven woman who passed away in August.

The two most recent outbreaks of EEE occurred between 2004-2006 and 2010-2012, during which 22 people were infected, 14 of whom were in Bristol and Plymouth counties, according to the state.

While a rare disease, EEE is lethal. Estimates of its fatality rate vary from 30-50 percent, with survivors often left with lasting and progressive neurological and physical problems, including personality disorders, intellectual impairment, paralysis, seizures and coma, according to the Centers for Disease Control and Prevention. Survivors of the initial infection often die within a few years.

Early symptoms include fever, chills, malaise and aches. After a few days, they may progress to headache, irritability, drowsiness, vomiting, diarrhea, convulsions and coma, according to the CDC.

West Nile

West Nile virus was found in mosquitoes in Truro in early August, and EEE was found there in late August, said Gabrielle Sakolsky, entomologist and assistant superintendent of the Cape Cod Mosquito Control Project.

Last year, there were 49 human cases of West Nile in Massachusetts, according to the state Department of Public Health.

“Last year was a banner year for West Nile; this year is a banner year for EEE,” said Sakolsky.

Unlike EEE, West Nile is usually much milder, and more common, and causes no symptoms in 80 percent of infected people, according to the state health department. Those with symptoms may have headache, nausea, vomiting, fever or a rash on their torso. About 1 percent of infected people will suffer inflammation of the brain (encephalitis) or its surrounding membranes (meningitis) with symptoms including high fever, stiff neck, headache, vision loss, disorientation, paralysis and coma. People 50 and older have a higher risk of developing severe symptoms.

While the latest round of mosquito sampling found none containing EEE or West Nile, “that doesn’t mean it’s not there,” Sakolsky said. Mosquitoes can persist until the first hard frost, and the viruses may remain in birds – the reservoir from which the insects pick up the diseases. Though mosquito activity slows with cooler weather, the mosquitoes active this fall are older and more likely to have been exposed to a virus, she said.

Ways to Be Vigilant

None of the Cape towns are considered by the state as at the lowest level of risk of EEE, or ‘remote,’ said Sakolsky. Bourne, Falmouth and Truro are listed at ‘moderate’ risk, and the remaining towns at ‘low’ risk.

She said that after Labor Day, “people tend to be more relaxed” about protecting themselves from mosquitoes. They shouldn’t be.

“Be vigilant!” Sakolsky said.

Dr. Oppenheimer urged schools to curtail nighttime athletic practices and events. She also said employers should caution workers against being outside at dusk or later and encourage them to use protective clothing and repellent. Landscapers, construction workers and others who routinely work outside are at higher risk.

To avoid being bitten, the state Bureau of Infectious Disease and Laboratory Services recommends these steps:

  • Stay indoors between dusk and dawn and schedule events during daylight hours.
  • Wear pants, socks and long-sleeved shirts.
  • Use an effective mosquito repellent, such as DEET, picaridin, oil of lemon eucalyptus and IR3535. Don’t use products containing DEET or oil of lemon eucalyptus on infants and children under 3. Use permethrin products on clothing and camping gear.
  • Keep your home’s window and door screens repaired to keep mosquitoes outside.
  • Remove standing water from around your home. Mosquitoes can breed in any standing water that lasts four days. Empty birdbaths, plant containers, wading pools and pool covers where water collects and keep gutters clear of debris. Aerate ornamental ponds or stock them with fish to eat mosquito larvae. Keep swimming pools chlorinated.

“People should still be alert,” Dr. Oppenheimer said, especially when near marshy land or bodies of water. On the Cape, no one is ever very far from either.