What is Eastern Equine Encephalitis?
Eastern equine encephalitis (EEE) is one of the most serious diseases passed on by insects, predominantly affecting the United States. It’s growing, impacting more people each year. Approximately six to eight cases are reported annually in the US. These cases are mostly noted between the months of May and October, and are mainly in states like Florida, Georgia, Maryland, Wisconsin, and New Jersey. It’s alarming to note that this virus might potentially be used as a means of biowarfare , as it can be transmitted through the air. The mortality rate is around 30%, with neurological problems seen in half the survivors.
What Causes Eastern Equine Encephalitis?
The Eastern equine encephalitis virus (EEEV) is a type of virus belonging to the Togaviridae family and the alphavirus genus. This virus mainly lives through a cycle involving birds and a kind of mosquito known as Culiseta melanura, which are often found near freshwater hardwood swamps.
Recent studies have suggested that other types of mosquitoes can also spread EEEV. These include Coquillettidia perturbans, Aedes cinereus, and Aedes canadensis. Mosquitoes become infected with the virus and then transmit it to others while feeding on the blood of birds that often perch on trees, as well as mammals, reptiles, and amphibians that cross their path.
From time to time, this virus can also infect so-called ‘dead-end’ hosts like humans, pigs, horses, or pheasants. They’re referred to as ‘dead-end’ hosts because, while the virus does infect them, their body doesn’t produce enough of it to then infect any mosquitoes that might feed on their blood.
It’s unpredictable when this cross-infection will occur, but changes in the weather and global warming seem to potentially influence this. Other factors that might affect this include changes in the environment, movements of birds, and human activity in the environment. Notably, in 2017, there was the first reported case of EEEV being transmitted through organ transplantation.
Risk Factors and Frequency for Eastern Equine Encephalitis
The Eastern equine encephalitis virus (EEEV), which affects the brain, was first seen in humans in 1938 during a significant outbreak in Massachusetts, U.S. Normally, humans do not play a role in the natural cycle of this disease but can sometimes be infected, particularly in regions along the Atlantic and Gulf coasts of the U.S.
The most substantial EEEV outbreak on record happened in 1959 in New Jersey, U.S., with 32 cases reported over eight weeks. Since 2003, the disease has been nationally notifiable and its monitored through ArboNET, a disease surveillance system for virus diseases transmitted by ticks and mosquitoes. The latest data shows EEEV has been found in 20 states. Its presence is highest in Massachusetts, Florida, and New Hampshire, but cases are now being reported in new states like Arkansas, Connecticut, Maine, Tennessee, North Carolina, and Vermont, increasing the geographical scope of this viral brain inflammation.
- The U.S. reports an average of eight EEEV cases each year.
- Compared to females, males are twice as likely to develop the severe form of the disease, where the virus spreads to the nervous system.
- The disease most often affects people under 5 or over 60 years of age.
- A study shows a dangerously high death rate of 41% for this disease. Additionally, 50% of those who recover may suffer long-term neurological damage.
Interestingly, reports indicate greater activity of EEEV among non-human species than what is suggested by human data. Researchers believe this could be due to several factors. For instance, the necessary conditions might not be present for the virus to move beyond its usual cycle among animals and cause an outbreak. Alternatively, the disparity could arise from weaknesses in disease surveillance or testing methods.
Signs and Symptoms of Eastern Equine Encephalitis
Human arboviral disease, when it causes symptoms, can lead to three different conditions. These are:
- Febrile systemic illness, like in ordinary Dengue fever
- Hemorrhagic fever, seen in severe cases of Dengue and yellow fever
- Encephalitis, which includes diseases like Venezuelan equine encephalitis, Japanese encephalitis, La Crosse encephalitis and Eastern Equine Encephalitis (EEE).
Around 96% of people infected with these diseases don’t show any symptoms. For the ones that do, the signs can be pretty general. They may experience fever, headaches, fatigue, chills, joint pain, nausea, and vomiting. Less than 5% of the infected people may develop severe conditions like meningitis or encephalitis. Neurological symptoms, like altered mental status and seizures, usually show up within the first five days. In some cases, patients have reported sensory disturbances and weakness in certain areas of the body.
A significant observation by many researchers is the connection between the duration of the prodromal (early) symptoms and the eventual outcome of the disease. Patients who experience a brief period of early symptoms tend to have a higher risk of death or neurological disabilities. In contrast, a milder or more prolonged early phase is often linked to full recovery or moderate disability, particularly in children.
Testing for Eastern Equine Encephalitis
When dealing with certain medical conditions, especially those affecting the brain, simple lab tests are often the first step. Doctors frequently look for signs of increased white blood cells in the body. Additionally, doctors may review cerebrospinal fluid (the fluid in your brain and spine), where they often find an increase in a kind of white blood cell called neutrophils.
However, certain more specific diagnostic tests, like a polymerase-chain-reaction analysis or serology (a blood test that looks for antibodies), may not show signs of illness when symptoms first start to show. These tests usually become positive within a week, often after neurological damage has already happened. Therefore, doctors recommend repeating these blood tests when brain inflammation is suspected due to a virus. Antibody levels can rise up to four times within just four days.
In cases where the cerebrospinal fluid does not test positive, doctors still pay attention to a blood test that shows positive antibodies as this could be an early sign of illness. Also, even when the initial tests are negative, doctors may repeat the tests to secure a definitive diagnosis when it isn’t possible to repeat a spinal tap. Both antibodies and virus-specific tests play important roles in identifying certain diseases, and ELISA and IFA are some of the testing techniques used.
Imaging results from MRI or CT scan can also assist with diagnosis. These scans can show problems in specific areas of the brain like the basal ganglia, thalamus, and the cerebral cortex (the outer layer of the brain). The brain MRI can reveal focal lesions (small areas of damage), without much swelling. This finding is different from what is typically seen in autopsy, where severe swelling is common and usually peaks around day 12 in 60% of patients with brain inflammation.
In children, the cortex seems to be the area of the brain most affected. The early involvement of the thalamus and basal ganglia (deep-seated parts of the brain) can help distinguish this condition from Herpes simplex encephalitis. While computerized tomography (CT scans) also commonly show lesions in the basal ganglia, MRI is the preferred imaging method, as it is more sensitive and can identify common changes.
Treatment Options for Eastern Equine Encephalitis
Presently, there is no antiviral medication that has been successful in treating Eastern equine encephalitis, a type of brain inflammation. The usual treatment involves supportive care, often in an intensive care unit where the patient can be assisted with breathing. These patients do not need to be isolated from others. Some patients with severe brain inflammation may need to have their brain pressure monitored regularly. If the pressure gets too high, it may be treated in a number of ways, even sometimes involving a surgical procedure to relieve pressure; this is usually a last resort for stubborn cases.
There have been a few reports suggesting that corticosteroid drugs, used to reduce inflammation, might lead to worse outcomes. In contrast, another report suggests that therapy using immunoglobulins, proteins used by the immune system to identify and neutralize foreign objects, may be beneficial.
Since there is currently no vaccine for this disease, the best approach is prevention. This includes efforts to reduce the number of insects that can spread the disease, such as by removing potential breeding sites and using insecticides. Individual people can also take preventive measures like wearing protective clothing and using insect repellents.
What else can Eastern Equine Encephalitis be?
In regions where the Eastern equine encephalitis virus is more likely to spread, doctors should include it as a possible diagnosis for cases of aseptic meningitis or encephalitis. Any suspected infections should also be reported to the local health department. Other potential diagnoses could include various forms of viral encephalitis, like those caused by measles, mumps, or echovirus. Diseases caused by prions, like Creutzfeldt–Jakob disease, are less likely but should also be considered.
What to expect with Eastern Equine Encephalitis
The fatality rate can reach up to 41%. About half of those affected are likely to develop some form of neurological disability. Certain factors can predict a poor outcome, such as severe low sodium levels in the blood, changes in brain electrical activity, and a high initial increase in the number of white blood cells in spinal fluid. These signs might indicate inflammation, interestingly, patients who were treated with drugs that reduce inflammation (corticosteroids) had worse outcomes than those who were not.
Possible Complications When Diagnosed with Eastern Equine Encephalitis
There are several possible complications from certain illnesses, many of which affect the central nervous system and can lead to problems with thinking, movement, or sensation. The most common associated problems include seizures (63% of cases), but it can also lead to paralysis, intellectual disability, and behavioral changes. If diagnosis and treatment are delayed, it can cause multiple organs to fail, problems with the nervous system controlling automatic bodily functions, and in severe cases, death. There was even a rare case where a 5 month-old baby developed a condition called hemophagocytic lymphohistiocytosis due to Eastern Equine Encephalitis (EEE). Some people also experienced behavior changes, like psychosis.
Common Complications:
- Problems with thinking, movement, or sensation
- Seizures
- Paralysis
- Intellectual disability
- Behavioral changes
- Multiple organs failing
- Problems with the nervous system controlling automatic bodily functions
- Possibility of death
- Hemophagocytic lymphohistiocytosis in rare cases
- Behavior changes, like psychosis
Preventing Eastern Equine Encephalitis
Eastern equine encephalitis is a disease caused by a virus that a certain type of mosquito carries, which is typically found in freshwater swamps. If you contract this virus, you may experience symptoms like fever, chills, headaches, and muscle and joint pains. To diagnose this disease, doctors will perform blood tests and a procedure called a lumbar puncture that allows them to test your cerebrospinal fluid. As of now, there is no direct treatment – doctors will monitor your condition closely and provide supportive care to alleviate symptoms.
Eastern equine encephalitis can be very serious. It may result in death in about 41% of the cases, highlighting the importance of early diagnosis. Moreover, up to 50% of patients may experience nervous system-related issues following infection, including seizures, paralysis, changes in behavior such as psychosis, and intellectual disability. Unfortunately, there are no vaccines available to prevent the disease.
Therefore, preventing exposure to mosquitos is critical to avoid getting the disease. The Center for Disease Control and Prevention (CDC) has a few recommendations to reduce the risk. These include using bug sprays with ingredients like DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone. They also suggest wearing long-sleeved shirts and long pants, and controlling the mosquito population both inside and outside of your home.
