This 2014 photo made available by the US Centers for Disease Control and Prevention shows a … [+]
A rare but potentially fatal virus – Eastern Equine Encephalitis – was identified in an 80-year-old man in Massachusettsprompting officials in several nearby towns to call for awareness and vigilance among community members to prevent additional cases. This is the first human case of HEE in Massachusetts since 2020, but the fourth documented case so far this year in the United States.
What is eastern equine encephalitis?
Eastern equine encephalitis, also known as EEE, is a virus that is transmitted to humans through the bite of an infected mosquito. The virus is endemic to the northeastern US and circulates naturally between mosquitoes and birds. After a mosquito bite, the virus can cause rare infections in humans and horses, which are considered dead-end hosts. This is because the virus cannot be passed on from an infected human or horse to a mosquito that can take a subsequent blood meal.
HEE cases are more common in the spring and summer months in the US, when the mosquito vector is most visible. Over the past 20 years, EEE has caused, on average, 9-10 human cases per year in the US.
What are the symptoms of EEE?
Most people infected with HEE have no symptoms. However, in about 30% of cases, symptoms can be severe and can lead to death. After an average incubation period of 4 to 10 days after a mosquito bite, an infected person may develop a fever, body aches, chills, and possibly joint pain. The infection can then lead to meningitis or encephalitis, which can lead to headache, confusion, seizures and coma. Among those who survive neurological disease after HEE infection, many go on to experience a range of physical and mental disorders, including seizures, mental challenges, and paralysis. Symptoms can be particularly severe in very young children and the elderly.
Are there vaccines or medications for IEE?
Unfortunately, there are no vaccines or antivirals specifically approved to prevent or treat EEE. In mild to moderate cases, patients are often treated with supportive care, including hydration and treatment with over-the-counter medications to manage pain and fever. In those who are hospitalized, more aggressive supportive care is often required. Antibiotics are not effective for treating HEE infection.
Are tests available to diagnose HEE?
Although testing for EHE is not routinely available, testing can be performed in selected clinical and public health laboratories. The diagnosis of HEE is usually based on clinical presentation—that is, a febrile illness with neurologic symptoms in a patient with recent mosquito exposure—with confirmation by serologic or molecular testing. Serological tests look for antibodies in the blood that have been made in response to infection. However, antibodies may take 1-2 weeks after infection to reach detectable levels. Molecular tests, or PCR, can be used to detect viral RNA in samples such as blood or cerebrospinal fluid.
Corn plants grow in standing water in a field. Stagnant water is a breeding ground for mosquitoes.
How can IEE infections be prevented?
In several Massachusetts towns near the recent human case, citizens are being asked to avoid going out after dark. This is because mosquitoes are more active after dark. Mosquito bites can also be reduced by using insect repellent and wearing long pants and shirts if it is necessary to be outdoors during periods of high mosquito activity.
It is also important to reduce the prevalence of mosquito breeding areas, which can include any location with standing water. Take the time to look around your property and make sure empty pots are turned over and old tires aren’t filling with standing water. These simple steps can help reduce transmission rates of EHE, along with other potentially serious mosquito-borne infections.
