Table of ContentsView AllTable of ContentsSymptomsTransmissionPrevalenceDiagnosisTreatmentPrognosisPrevention
Table of ContentsView All
View All
Table of Contents
Symptoms
Transmission
Prevalence
Diagnosis
Treatment
Prognosis
Prevention
Some people infected with EEE have no symptoms, while others develop a fever and make a full recovery. Approximately 5% of people who get EEE developencephalitis, which is inflammation of the brain.About one in three people who develop encephalitis due to EEE die. Half of those who survive have permanent neurological damage.
This article explains the signs and symptoms of eastern equine encephalitis. It covers how the disease is diagnosed and treated, the mortality risk associated with EEE, and how to protect yourself from EEEV infection.
How rare is Eastern equine encephalitis?In the United States, there are less than 15 documented cases per year.
How rare is Eastern equine encephalitis?
In the United States, there are less than 15 documented cases per year.
Sitikka / Getty Images
What Are the Symptoms of Eastern Equine Encephalitis?
Many people who infected with EEEV don’t have symptoms (are asymptotic).If they do begin to feel sick, the severity of the illness will depend on individual factors, such as their age and their overall state of health.
EEEV can cause two different forms of illness: systemic and encephalitic.The systemic form of the illness is generally less severe. When EEE reaches the brain (the encephalitic form) the resulting illness can be fatal.
Systemic EEE Symptoms
The systemic form of EEE looks and feels like amild case of the flu. Symptoms include:
Encephalitic EEE Symptoms
Encephalitic EEE is the more severe form and is often fatal.This form usually begins with the sudden and severe onset of a headache, high fever, chills, and vomiting.
As the virus migrates to the brain, it causes brain tissues to inflame and swell. This is encephalitis, which can rapidly lead to severe neurological symptoms, including:
A person with encephalitic EEE can fall into a coma as soon as four days after being infected with EEE.
Cases of EEE affecting the brain are more frequent in males than females. According to the CDC, severe illness is most likely to occur in people younger than 15 or older than 50, as well as people who have compromised immune systems.
Can Humans Get EEEV From Horses?
Brain Infection Symptoms and Treatment
How Is EEEV Transmitted?
From there, the virus passes from these mosquitos to the birds they feed on, most of which live in swampy areas.C. melanura, C. mortisans,and birds don’t directly infect humans with EEEV.
The virus can only continue to spread if another species of mosquito that feeds on birds and mammals (such asAedes)becomes a “bridge vector.” The transmission cycle can continue when one of these mosquitos bites an infected bird, then bites a horse or human.
Once the virus finds a horse or human host, it doesn’t continue to spread.The levels of the virus in the body of a human or horse with EEEV aren’t enough to infect more mosquitos, which would be necessary to continue the transmission cycle.
A person infected with EEEV can’t spread it to another human and humans can’t catch the virus from contact with a sick animal—with one possible exception.
In rare cases of EEE in emus, there may be an increased risk of transmission. Emus often experience bloody diarrhea from the infection which may be capable of spreading the virus. Animals or human caretakers who touch an emu’s infected blood or feces may be at risk for contracting EEEV.
Prevalence of EEEV Infection
Cases of EEE are very rare in the United States. From 2009 to 2018 there was an average of seven cases reported each year (a range from three to 15). These cases were concentrated in states where EEEV is endemic, including:
EEE in humans has also appeared sporadically throughout New England and the Gulf Coast. Maine, New Hampshire, and Georgia have also seen multiple cases in the last decade.
The exact incidence of EEE in the U.S. may be higher than the statistics imply. EEE is a notifiable disease and states are encouraged to inform the CDC of confirmed human cases.However, because most people who are infected with EEEV have no or only mild symptoms, they are unlikely to seek medical care and be tested for the virus.
Outside of the U.S., cases of EEE have been found in animals throughout Central and South America as well as the Caribbean. While EEEV has been isolated in these regions, it’s not uncommon for human cases to be tied back to someone who traveled to an area of the U.S. where the virus is endemic.
Statistics indicate that EEEV is most active in July, August, and September.
Who Is Most at Risk for EEEV Infection?As is usually true of mostinfectious illnesses, infants, seniors, and anyone with a compromised immune system are more likely to experience severe illness if they are infected with EEEV.People in these groups are also at greater risk of developing complications from EEE, including death.
Who Is Most at Risk for EEEV Infection?
As is usually true of mostinfectious illnesses, infants, seniors, and anyone with a compromised immune system are more likely to experience severe illness if they are infected with EEEV.People in these groups are also at greater risk of developing complications from EEE, including death.
Diagnosing EEE
When more common conditions have been ruled out, doctors working in areas where EEEV is known to lurk may consider more invasive tests—especially if other cases of EEE have recently been reported.
Inflammation and swelling in the brain may be visible on aCT scanorMRI. If a doctor has ruled out other explanations for these symptoms, the next step will be to test for EEEV.
There may be signs of inflammation or EEEV antibodies present in a person’s blood and spinal fluid. If blood tests do not provide enough information, a doctor may need to perform a lumbar puncture (also called a “spinal tap”) to get spinal fluid for testing.
During a spinal tap, a needle is inserted into the lower back. Then, a small amount of fluid from the spinal canal is drained into a vial which can be sent to a lab and examined for EEEV.
Compared to more common pathogens, it can be difficult to determine if EEEV is present in a sample.Therefore, the sample must be tested in a lab that has the technology to examine it for EEEV antibodies.
In states where EEE is known to occur, labs are more likely to be equipped to perform the tests. Healthcare providers can also work with the state health department or send samples to the CDC for testing.
In some cases, a diagnosis of EEE may not be confirmed until after a person has died and their brain tissue tested as part of anautopsy.
All confirmed cases of EEE need to be reported. Public health departments in each state collect data on infectious diseases and report it to the CDC each year.
Autoimmune Encephalitis: From Symptoms to Treatment
Can Eastern Equine Encephalitis Be Cured?
There is no cure for EEE and noantiviral medicationspecific for EEEV has been developed.As with other viral illnesses,antibioticsare not effective for treating EEE.
The amount of medical care a person with EEE needs will depend on how sick they are, as well as their individual risk factors. Infants and older adults, those with another medical condition, or people with weakenedimmune systemsare more likely to become seriously ill.
By contrast, an otherwise healthy young adult may have mild symptoms that resolve on their own and don’t even warrant a call to their doctor.
People with the encephalitic form of EEE almost always require hospitalization. There, they can be tested for EEEV and receive medical care to ease their symptoms. They may need to be admitted to the intensive care unit and put on a respirator or into a medically induced coma to allow their body to try to fight the virus.
Intravenous fluids may be used to rehydrate someone, while antipyretics can reduce fever. Treatment with IVIg (intravenous immunoglobin) has yielded mixed results and needs more study. Case reports have variably shown steroids to help or hurt outcomes, but they can theoretically reduce inflammation and brain swelling.
Signs of a Bacterial or Viral Infection
Mortality Risk and Prognosis
One out of every three people with the severe form of EEE will die.As the virus infiltrates the brain, the illness becomes rapidly and progressively worse. Once symptoms develop, a person may die within four to 10 days.
If someone survives a major EEE infection, they often have permanent symptoms and may become disabled. Neurological damage from the virus has been shown to cause physical and mental illness for those who survive the infection.
The long-term health of these individuals is often compromised; many people who develop severe EEEV infections will die within a few years of getting sick with EEE.
While there may not be a cure, specific course of treatment, or vaccine, there are steps you can take to reduce your risk of contracting EEEV.
If you live, work, or participate in outdoor recreation in states where EEEV has been identified, be especially mindful of when mosquitoes are most active. For example, in the summer months of the year and at dawn or dusk.
Making sure all windows in your home have screens and that your yard is free of standing water can also reduce your exposure to mosquitoes.
Summary
Eastern equine encephalitis (EEE) is rare in humans. People infected with the virus may have no symptoms, mild symptoms, or severe life-threatening illness. Although EEE can also infect horses, people can’t catch the virus from a horse or another mammal—including humans. One in three people who contract EEE will die and those who survive often become permanently disabled.
14 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About eastern equine encephalitis.Yale Medicine.Eastern equine encephalitis (EEE) is back—should you be worried?.Lindsey NP, Staples JE, Fischer M.Eastern equine encephalitis virus in the United States, 2003–2016.ASTMH. 2018 Jan;98(5):1472-1477. doi:10.4269/ajtmh.17-0927Centers for Disease Control and Prevention.Symptoms & Treatment | Eastern Equine Encephalitis.Massachusetts Department of Public Health and the Massachusetts Department of Agricultural Resources.WNV And EEE In Animals.Mass.gov.WNV and EEE in animals.Vector Disease Control International.Eastern equine encephalitis virus: public health, mosquito management.Centers for Disease Control and Prevention.Statistics & Maps | Eastern Equine Encephalitis.American Association of Equine Practitioners.Eastern / western equine encephalomyelitis | Core vaccination guidelines.Centers for Disease Control and Prevention.Bacterial meningitis.Barba M, Fairbanks EL, Daly J.Equine viral encephalitis: prevalence, impact, and management strategies.VMRR. 2019 Jul;10(1):99-110. doi:10.2147/VMRR.S168227Centers for Disease Control and Prevention.Diagnostic testing.Centers for Disease Control and Prevention.Specimen submission instructions and reagent ordering forms.Centers for Disease Control and Prevention.Prevention.Additional ReadingCarrera JP, Forrester N, Wang E, et al.Eastern equine encephalitis in Latin America. N Engl J Med. 2013;369(8):732-44. doi:10.1056/NEJMoa1212628Centers for Disease Control and Prevention.Specimen Submission Instructions And Reagent Ordering Forms.State of New Hampshire Department of Health and Human Services, Division of Public Health Services.West Nile Virus and Eastern Equine Encephalitis in Dogs and Cats.
14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About eastern equine encephalitis.Yale Medicine.Eastern equine encephalitis (EEE) is back—should you be worried?.Lindsey NP, Staples JE, Fischer M.Eastern equine encephalitis virus in the United States, 2003–2016.ASTMH. 2018 Jan;98(5):1472-1477. doi:10.4269/ajtmh.17-0927Centers for Disease Control and Prevention.Symptoms & Treatment | Eastern Equine Encephalitis.Massachusetts Department of Public Health and the Massachusetts Department of Agricultural Resources.WNV And EEE In Animals.Mass.gov.WNV and EEE in animals.Vector Disease Control International.Eastern equine encephalitis virus: public health, mosquito management.Centers for Disease Control and Prevention.Statistics & Maps | Eastern Equine Encephalitis.American Association of Equine Practitioners.Eastern / western equine encephalomyelitis | Core vaccination guidelines.Centers for Disease Control and Prevention.Bacterial meningitis.Barba M, Fairbanks EL, Daly J.Equine viral encephalitis: prevalence, impact, and management strategies.VMRR. 2019 Jul;10(1):99-110. doi:10.2147/VMRR.S168227Centers for Disease Control and Prevention.Diagnostic testing.Centers for Disease Control and Prevention.Specimen submission instructions and reagent ordering forms.Centers for Disease Control and Prevention.Prevention.Additional ReadingCarrera JP, Forrester N, Wang E, et al.Eastern equine encephalitis in Latin America. N Engl J Med. 2013;369(8):732-44. doi:10.1056/NEJMoa1212628Centers for Disease Control and Prevention.Specimen Submission Instructions And Reagent Ordering Forms.State of New Hampshire Department of Health and Human Services, Division of Public Health Services.West Nile Virus and Eastern Equine Encephalitis in Dogs and Cats.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Centers for Disease Control and Prevention.About eastern equine encephalitis.Yale Medicine.Eastern equine encephalitis (EEE) is back—should you be worried?.Lindsey NP, Staples JE, Fischer M.Eastern equine encephalitis virus in the United States, 2003–2016.ASTMH. 2018 Jan;98(5):1472-1477. doi:10.4269/ajtmh.17-0927Centers for Disease Control and Prevention.Symptoms & Treatment | Eastern Equine Encephalitis.Massachusetts Department of Public Health and the Massachusetts Department of Agricultural Resources.WNV And EEE In Animals.Mass.gov.WNV and EEE in animals.Vector Disease Control International.Eastern equine encephalitis virus: public health, mosquito management.Centers for Disease Control and Prevention.Statistics & Maps | Eastern Equine Encephalitis.American Association of Equine Practitioners.Eastern / western equine encephalomyelitis | Core vaccination guidelines.Centers for Disease Control and Prevention.Bacterial meningitis.Barba M, Fairbanks EL, Daly J.Equine viral encephalitis: prevalence, impact, and management strategies.VMRR. 2019 Jul;10(1):99-110. doi:10.2147/VMRR.S168227Centers for Disease Control and Prevention.Diagnostic testing.Centers for Disease Control and Prevention.Specimen submission instructions and reagent ordering forms.Centers for Disease Control and Prevention.Prevention.
Centers for Disease Control and Prevention.About eastern equine encephalitis.
Yale Medicine.Eastern equine encephalitis (EEE) is back—should you be worried?.
Lindsey NP, Staples JE, Fischer M.Eastern equine encephalitis virus in the United States, 2003–2016.ASTMH. 2018 Jan;98(5):1472-1477. doi:10.4269/ajtmh.17-0927
Centers for Disease Control and Prevention.Symptoms & Treatment | Eastern Equine Encephalitis.
Massachusetts Department of Public Health and the Massachusetts Department of Agricultural Resources.WNV And EEE In Animals.
Mass.gov.WNV and EEE in animals.
Vector Disease Control International.Eastern equine encephalitis virus: public health, mosquito management.
Centers for Disease Control and Prevention.Statistics & Maps | Eastern Equine Encephalitis.
American Association of Equine Practitioners.Eastern / western equine encephalomyelitis | Core vaccination guidelines.
Centers for Disease Control and Prevention.Bacterial meningitis.
Barba M, Fairbanks EL, Daly J.Equine viral encephalitis: prevalence, impact, and management strategies.VMRR. 2019 Jul;10(1):99-110. doi:10.2147/VMRR.S168227
Centers for Disease Control and Prevention.Diagnostic testing.
Centers for Disease Control and Prevention.Specimen submission instructions and reagent ordering forms.
Centers for Disease Control and Prevention.Prevention.
Carrera JP, Forrester N, Wang E, et al.Eastern equine encephalitis in Latin America. N Engl J Med. 2013;369(8):732-44. doi:10.1056/NEJMoa1212628Centers for Disease Control and Prevention.Specimen Submission Instructions And Reagent Ordering Forms.State of New Hampshire Department of Health and Human Services, Division of Public Health Services.West Nile Virus and Eastern Equine Encephalitis in Dogs and Cats.
Carrera JP, Forrester N, Wang E, et al.Eastern equine encephalitis in Latin America. N Engl J Med. 2013;369(8):732-44. doi:10.1056/NEJMoa1212628
Centers for Disease Control and Prevention.Specimen Submission Instructions And Reagent Ordering Forms.
State of New Hampshire Department of Health and Human Services, Division of Public Health Services.West Nile Virus and Eastern Equine Encephalitis in Dogs and Cats.
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