Eastern Equine Encephalitis

By Dr. Brian Irwin

Given our location in the heart of the "mosquito belt," New Hampshire residents are no strangers to seasonal insects. These annoying nuisances, unfortunately, do not just leave behind an itchy bite or a red blotch on the skin; they can leave behind aggressive, sometimes debilitating diseases that they may transmit during their bite. One of these diseases is Eastern Equine Encephalitis, or EEE.Eastern Equine Encephalitis is caused by a virus closely related to the viruses that cause the similar Western Equine Encephalitis. These viruses have been known threats since their recognition dating back to the 1960s. At that time these viruses were thought to be only threats to horses, which were the first animals known to be infected with EEE and WEE. In 1964, however, EEE was first reported in a case of human encephalitis. The Centers for Disease Control has been tracking EEE since this time; however, there were only 200 reported cases from 1964 to 2003. Curiously, the incidence of EEE has seemed to increase dramatically in the last few years, bringing it into the spotlight as an up-and-coming threat that everyone needs to be aware of.Before this year there had never been a reported death from EEE in the state of New Hampshire, but this year the first death from this virulent virus occurred. It isn't clear if the virus is indeed "spreading," or if the appearance of a small handful of cases in New Hampshire was a fluke, but, regardless, the local presence of this virus makes it important to understand.The virus that causes EEE is carried and transmitted by mosquitos. While they are the vector, birds are the primary host who become infected with EEE virus, passing it along to mosquitos who feed on their carcasses, who then in turn pass it on to more birds. During that cycle, a mosquito bite to a human or horse transmits the disease and can result in infection. Typically the infection presents with vague, flu-like symptoms. Between two days and two weeks after infection, most cases experience body aches, fatigue and nausea. A fever, up to 106 degrees, can be present. Many cases, probably many undiagnosed, run the course of this syndrome and resolve. However, a more severe form of the disease is possible: Encephalitis.Not all infections by the EEE virus cause true encephalitis, which is infection of the brain itself (as opposed to meningitis, which is infection of the membrane that covers the brain). However severe cases that do go on to become encephalitis carry an astounding 35 percent death rate. Further, 35 percent of patients who survive suffer permanent neurologic deficits. This severe form presents with the same vague findings mentioned above, but also often has an extreme headache, stiff neck, double vision and even coma.There is no cure for EEE, and the mainstay of treatment is supportive, whether this means mechanical ventilator support, IV fluids or rehabilitation. Prevention is, at this stage, most important for the public to realize. First, know if you?re high risk. People over age 50 and younger than age 15 are at greatest risk for the severe form of the disease. People who work in the outdoors are also at significantly increased risk. Secondly, if you are at risk (and perhaps even if you're not) protect yourself. Wear DEET to prevent mosquito bites. Wear protective clothing. Avoid areas of standing water where mosquito pools may exist. And perhaps most importantly, be on the lookout for symptoms, and, if you have any, call your health-care provider as soon as possible. EEE is a scary, aggressive disease, but through proper prevention and proper education you can protect yourself, your family and hopefully avoid this dangerous condition.Dr. Brian Irwin practices at Saco River Medical Group in Conway.