Eastern Equine Encephalitis (EEE)

  • Avoiding insect bites: what parents should know

    Read more about preventing mosquito bites in the article Insect spread illnesses on the rise: how to protect your family posted on Thriving, Boston Children’s Hospital’s pediatric health blog.


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  • In-Depth


    What causes Eastern Equine Encephalitis (EEE)?

    Eastern Equine Encephalitis (EEE) belongs to a category of viruses known as arboviruses, or arthropod-borne viruses. Arboviruses are spread by the bites of blood-sucking insects, such as mosquitos and ticks. EEE is spread by the bite of certain kinds of mosquitoes. 

    Risk factors

    The overall risk of becoming infected with Eastern Equine Encephalitis (EEE) depends on:

    • Exposure to mosquitoes: People who spend a lot of time outdoors or live in wooded areas have a greater chance of being bitten by mosquito.
    • Time of year and day: In the United States, cases of EEE tend to occur from late spring to early fall.. Many kinds of mosquitoes are most active during dusk and dawn and during the early evening hours. 
    • Geographic region: Most cases of EEE have been reported in Atlantic and Gulf coast states. Southeastern Massachusetts, particularly Plymouth and Bristol counties, have historically been ‘hot spots’ for EEE. The Massachusetts Dept of Public Health monitors mosquito populations, tests mosquitoes for virus and calculates risks for each town.

    Some people with EEE may develop a severe infection that causes brain tissue to become inflamed (encephalitis).The factors that increase one’s risk of getting a severe EEE infection include:

    • Age: Although people of any age can develop a serious infection, the risk is higher for adults older than 50 and children younger than 15.
    • Immune system: People who have a weakened immune system due to cancer treatments, or organ transplantation are more at risk of developing a serve infection.


    What are the symptoms of Eastern Equine Encephalitis (EEE)?

    Symptoms of EEE generally occur four to 10 days after a person has been infected and include:

    The symptoms of encephalitis depend on the part of the brain that is inflamed, the amount of inflammation and the person’s age and overall health.

    Some of the most common symptoms of encephalitis include:

    • Seizures
    • Confusion (disorientation)
    • Coma

    In one-third of cases, encephalitis can be fatal or lead to permanent brain damage.

    When to see a doctor

    Because the initial symptoms of EEE resemble those caused by many illnesses, it may be difficult to determine if a child’s symptoms are related to encephalitis. In general, you should take your child to see a doctor if your child has a bad headache, nausea and vomiting, fever or any worrisome changes in behavior (confusion, extreme sleepiness, acting very different, listlessness, lethargy, seizures). 

  • Tests


    How is Eastern Equine Encephalitis (EEE) diagnosed?

    A diagnosis of Eastern Equine Encephalitis (EEE) can be made using:

    • Blood tests. Someone who is infected with EEE will have an increased level of antibodies in their blood. Antibodies are proteins produced by the immune system that attack foreign substances such as viruses and bacteria. Increased levels of antibodies are a sign that your immune system is fighting the virus.  
    • A CT scan produces detailed, cross-sectional images of the brain. The results from a CT scan can rule out other possible diseases that may be causing inflammation.
    • A lumbar puncture (spinal tap)may be used to take a small sample of cerebral spinal fluid to determine if a child has EEE or other problems.
    • An electroencephalogram (EEG) can be used to detect small seizures in the brain that may not be obvious from watching the person. An EEG works by recording the brain's continuous electrical activity using stickers attached to the scalp that measure electrical activity.
    • A needle biopsy may be used to take a sample of brain tissue to determine the underlying cause of the inflammation.

  • Treatment options 

    How is Eastern Equine Encephalitis (EEE) treated?

    Although there is no specific treatment for Eastern Equine Encephalitis (EEE), there are several things that can be done to help manage the symptoms of the disease:

    • Anticonvulsants for seizures
    • Respirator for breathing problems
    • Pain relievers for headache, fever or body ache
    • Sedatives for irritability or restlessness
    • Corticosteroids for brain swelling


    How can I prevent EEE?

    Avoiding mosquito bites is the easiest and most effective way to prevent EEE. Listed bellows are some ways you can protect your children:

    • Dress them in socks, pants and long-sleeved shirts that cover their skin. 
    • Avoid areas where and when mosquitoes are abundant.
    • Install and fix window screens to prevent mosquitoes from entering your home. 
    • Empty buckets, toys and other items that hold water in which mosquitoes develop.
    • Make sure your roof gutters are clean of leaves and drain well.
    • Contact your local mosquito control district to learn of other options to reduce mosquito problems. 
    • Use insect repellents carefully and wisely.

    The easiest and most effective way to avoid mosquito bites is by using insect repellant. There are many products that are made to prevent mosquito bites. Experts from the American Academy of Pediatrics (AAP)  recommend one that can be applied directly to the skin that is particularly effective: DEET (usually listed on labels as N,N-diethyl-m-toluamide).

    The amount of DEET in insect repellents varies and may range from less than 10 percent to more than 30 percent. Products with higher concentrations of DEET tend to provide longer protection and need to be applied less frequently. According to the AAP, products that have around 10 percent DEET may keep away insects for nearly 2 hours, while products with about 24 percent DEET last an average of 5 hours.

    Other repellents contain yet other active ingredients (other than DEET). Select a repellent that is registered with the US EPA. Read and follow directions to use them properly. The AAP does not recommend insect repellants for children younger than 2 months.  

    Insect repellent 

    Here are additional do's and don'ts on how to use insect repellent:

    • DO apply repellent to all exposed skin areas and to clothing.
    • DO spray repellent in your hands first and then gently rub it on a child's face, avoiding the eyes and mouth.
    • DO use aerosols and pump sprays to ensure that the repellant is applied evenly.
    • DO use repellants with higher concentrations if there will be a long time between applications or if you will be in environments where mosquito populations are high.
    • DO wash repellent off once you get back indoors.
    • DON'T use insect repellent on skin that is already covered by clothing.
    • DON'T apply repellant directly onto a child's face.
    • DON'T keep using a repellent if it gives you a rash or other skin reaction.
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