Update, 4:35 p.m. ET: This story, originally published at 2:14 p.m., has been updated with information about a fatal case of EEE in New Hampshire.
A rare but deadly virus—eastern equine encephalitis—has been detected in two adult patients this week, one an 80-year-old man in Massachusetts and the other a resident of New Hampshire who has reportedly has died of the infection. Officials in northeastern states are calling for awareness and vigilance among community members to prevent additional cases. So far this year, there have been four documented cases in the United States.
What Is Eastern Equine Encephalitis?
Eastern equine encephalitis, also known as EEE, is a virus that is spread to humans through the bite of an infected mosquito. The virus is endemic in the northeastern U.S., and circulates naturally between mosquitoes and birds. Following a mosquito bite, the virus can cause rare infections in humans and horses, which are considered dead-end hosts. This is because it cannot be further spread from an infected human or horse to a mosquito that may take a subsequent blood meal.
Cases of EEE are most common in the spring and summer months in the U.S., when the mosquito-vector is most prominent. Over the past 20 years, EEE has caused, on average, nine to 10 human cases per year in the U.S.
What Are The Symptoms Of EEE?
Most individuals who are infected with EEE do not develop any symptoms. However, in about 30% of cases, symptoms can be severe and may lead to death. Following an average incubation period of four to 10 days after a mosquito bite, an infected person can develop a fever, body aches, shaking, chills and possibly joint pain. Subsequently, the infection can lead to meningitis or encephalitis, which can result in a headache, confusion, seizures and coma. Among those who survive neurologic disease following infection with EEE, many continue to experience a range of physical and mental disorders, including seizures, intellectual challenges and paralysis. Symptoms can be especially severe in very young children and the elderly.
Are There Vaccines Or Medications For EEE?
Unfortunately, there are no vaccines or antivirals specifically approved for preventing or treating 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 the treatment of EEE infection.
Are Tests Available To Diagnose EEE?
Although tests for EEE are not commonly available, select clinical and public health laboratories can perform testing. The diagnosis of EEE is usually based on the clinical presentation—i.e., a febrile illness with neurologic symptoms in a patient with recent mosquito exposure—with confirmation by serology or molecular testing. Serology tests look for antibodies in the blood that have been generated in response to the infection; however, antibodies may take one to two weeks after infection to reach detectable levels. Molecular, or PCR, tests can be used to detect viral RNA in samples, such as blood or cerebrospinal fluid.
How To Prevent EEE Infections
In towns near the recent human cases, officials are urging citizens to avoid going outside after dusk. This is because mosquitoes are most active after dark. People can also avoid mosquito bites by using insect repellant and wearing long pants and shirts if they must be outdoors during times when mosquitos are active.
It’s also important to reduce the prevalence of mosquito breeding areas, which can include any location with standing water. Take time to look around your property and ensure that empty planting pots are turned upside down and old tires aren’t filled with standing water. These simple steps can help reduce the rates of transmission of EEE, along with other potentially severe mosquito-borne infections.
