The scientific facts behind Eastern Equine Encephalitis virus (EEE)

By Staff Writer Maddie Kenn

Students and faculty are preparing themselves for the outbreak of Eastern Equine Encephalitis, commonly known by its abbreviation, EEE in the Dartmouth area. Staff writers for the Torch were able to meet with professor Bromage, an immunologist here on campus to discuss the virus and what community members can do to avoid getting infected.

The virus is known to be spread by mosquitoes, but what a majority of people are unfamiliar with, is that the main host of EEE is actually birds. Mosquitoes are just the vehicle the EEE virus uses to jump from bird-to-bird.

Occasionally, a mosquito that prefers a bird-blood meal also likes to snack on slightly bigger things, like goats, horses, and humans. It’s under these circumstances, a mosquito that feeds on an EEE-infected bird and then later feeds on a human, that the virus can be transmitted to people. However, the transmission of the virus from mosquitoes to humans is difficult, with transmission rates reported to be as low as three to five percent.

Given the threat mosquito-transmitted viruses pose to MA residents an extensive mosquito-monitoring program has been developed. Mosquito traps are set up all over the state, sampled twice every week throughout Summer and Fall, and tested for the presence of the EEE virus. The presence or absence of the EEE virus in those samples determines the risk level for that region.

Other factors, such as the presence of EEE infection in people or livestock, also influence the risk level of that region. When mosquitoes test negative for the virus, and there are no animal cases in the area, then the area is designated ‘no risk.’ If there are many EEE-carrying mosquitoes detected, or there is an EEE-infection in humans or livestock, then those areas are designated as ‘high’ or ‘critical.’

The Dartmouth area is categorized as a moderate risk for EEE as mosquitoes from a trap in Dartmouth tested positive for the virus in August. Although this may sound alarming, there is no need for panic, just caution.

A major misconception is that infection with the EEE virus often results in death. This is not true. Most people bitten by an infected mosquito will be asymptomatic – you will not even know you were infected. Some people exhibit mild flu-like symptoms with fever and chills, but fully recover in a few days.

Once recovered, you will have life-long immunity to the EEE virus. It is only in rare circumstances, where exposure to the EEE virus leads to a severe body-wide infection, does the person develop encephalitis (swelling of the brain), and the prognosis for recovery is poor.

As of right now, there have been no human or animal EEE cases reported in the Dartmouth area and there is not a high prevalence of EEE infected mosquitoes detected in the traps in our town. But our neighboring towns of New Bedford and Fairhaven are listed as critical. So there is good reason to be cautious in our approach to our personal safety.

Professor Bromage highly recommends reviewing the EEE risk map published weekly by Massachusetts Department of Public Health. The map contains crucial information such as color codes of where the virus has been found, what it means, risk factors, and what can be done in order to prevent yourself from being infected.

At this stage, with Dartmouth being categorized as a moderate risk, the guide recommends wearing mosquito repellent if you are outdoors and to adjust activities if you notice mosquito activity. If our risk were to increase, we would have to start thinking about modifying outdoor evening activities. Dr. Bromage notes that the Dartmouth Board of Health and the University have been very good at notifying their constituents of the risk the EEE virus poses to the community. So be personally vigilant, but know people are constantly monitoring the risk.

The important takeaway is to not panic. The EEE virus was first recognized in Massachusetts in 1831, so we have been living alongside this virus for a very long time. We just need to take appropriate precautions when spending time outdoors. Stay safe and have fun! Also, remember that the risk will disappear in three to four weeks when we have our first evening frost. Professor Bromage says that “most mosquitoes won’t survive the cold weather and chance of infection is almost eliminated……. until next summer!”



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