# 6501
While West Nile Virus is making headlines in Texas and across much of the nation, another mosquito-borne virus – EEE (Eastern Equine Encephalitis) – has the attention of Massachusetts health officials.
On Thursday, the Massachusetts Department of Health & Human Services released the following alert:
State Health Officials Raise EEE Threat Level in Two Communities after Detection of EEE-Positive Mosquitoes
New Bedford and Westborough raised to High; ground spraying to be enhanced
BOSTON — Thursday, August 16, 2012 – The Massachusetts Department of Public Health (DPH) today announced the detection of mammal-biting mosquitoes infected with Eastern Equine Encephalitis (EEE) in New Bedford and Westborough. As a result, health officials have raised the EEE threat level to “High” in these two communities and recommend that outdoor evening events are curtailed there for the remainder of the summer. Ground-based spraying by mosquito control projects is ongoing in both New Bedford and Westborough and will be enhanced.
So far, only one human case of EEE has been detected in Massachusetts this year, and that one is believed to have been acquired out of state. This risk of seeing additional cases, however, is deemed high in communities where human-biting mosquitoes are found to carry the virus.
Although far less common than West Nile Virus, EEE is of concern because it has a high fatality rate (35%), and among the survivors, a large number suffer ongoing neurological problems.
Over the past decade there have been an average of about 7 cases (not deaths) of `Triple E’ in the United States each year (range range: 3—21), which makes EEE an exceedingly rare disease in humans.
But given its severity (and the co-circulation of other mosquito borne diseases like West Nile, La Cross Virus, & SLEV), it makes sense to take steps to protect against mosquito bites – even if your local officials have not issued a warning.
The Florida Department of Health’s advice to protect against mosquito borne diseases is that people should practice the "5 D's"
Don't go outdoors at DUSK and DAWN when mosquitoes are most active.
DRESS so your skin is covered with clothing
Apply mosquito repellent containing DEET to bare skin and clothing.
Other effective repellents include picaridin, oil of lemon eucalyptus, and IR3535
Empty containers and DRAIN standing water around your home where mosquitoes can lay eggs.
While the number of yearly cases is low, the distribution of EEE in the United States far ranging.
The natural host for the EEE virus are songbirds, which can become infected usually without suffering ill effect. The virus is spread among these birds by the blood feeding of female mosquitoes (males don’t bite).
After an infected mosquito feeds on a bird, the bird becomes infected and the virus begins reproducing. After a few days, and for only a few days, the bird’s bloodstream amplifies the virus enough to infect subsequent mosquitoes that feed on it.
Culiseta melanura, which means "curly black hairs", is the species of swamp mosquito that serves as the primary vector for this virus among birds.
Culiseta melanura, however, isn’t usually attracted to humans.
So it generally requires a secondary type of mosquito - one that isn’t quite as picky a feeder - such as the Aedes albopictus or Coquillettidia perturbans `salt and pepper’ mosquito, to bite an infected bird in order to move it into the equine or human population.
The Transmission cycle is illustrated by the following graphic from the CDC.
Humans and horses don’t develop a high enough viral EEE titer in their bloodstream to pass on the virus if they are subsequently bitten by a mosquito, so they are considered to be `dead-end hosts’.
As there is no vaccine against EEE, the best tactic is prevention, and high in that category is the use of mosquito repellants.
To help you with choosing the right repellant the EPA has developed an interactive insect repellant search engine that will that will allow you to input your needs and it will spit out the best repellants to use.
(click image to go to search engine)
For more on Arboviruses in the United States you may wish to revisit this blog from last year:
MMWR: Arboviral Disease Surveillance – 2010
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