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Eastern Equine Encephalitis Virus

Public Notice: Eastern equine encephalitis detected in northern Indiana

The Centers for Disease Control and Prevention (CDC) has confirmed to Indiana health officials that a Hoosier in Elkhart County contracted eastern equine encephalitis, or EEE, a rare virus transmitted by mosquitoes. The patient died as a result of the infection.

This is the first human case in Indiana since 1998 and only the fourth reported since 1964. The CDC says approximately 5 to 10 human cases of EEE are reported nationwide each year, typically from late spring through early fall. Nearly one-third of human cases are fatal.

“It’s hard to imagine losing a loved one because of a mosquito bite, but unfortunately, mosquitoes carry diseases that can be life-threatening,” said State Health Commissioner Kris Box, M.D., FACOG. “This is a tragic loss for an Indiana family.”

The Elkhart, LaGrange and Noble county health departments and the Indiana State Department of Health (ISDH) have been working together to monitor EEE activity.


Due to the detection of EEE activity in the area and the occurrence of human EEE cases in nearby Michigan counties, health officials performed targeted mosquito control Wednesday night, Oct. 2, utilizing aerial spraying to help protect residents from EEE. On Thursday evening, Oct. 3, a second treatment was made in LaGrange and Noble counties to complete the application. While rare, EEE virus can cause serious illness and has a fatality rate of about 33 percent in people.


Mosquito control professionals applied an approved pesticide, Dibrom, as an ultra-low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets that stay suspended in the air and kill adult mosquitoes on contact. Dibrom has been registered by the U.S. Environmental Protection Agency (EPA) since 1959 for use in the United States. Dibrom immediately begins to break down upon release of the spray droplets in the open air and breaks down rapidly in water and in sunlight.


Protecting public health is the primary goal of the decision. The spray area is centered around the area where equine cases have been confirmed. This activity is not expected to pose a risk to humans.


While the spraying is expected to kill 90 percent of mosquitoes, residents in the area are urged to continue to take precautions until the first hard freeze. Click here for more information about other preventive measures.


For more information about EEE, visit the CDC’s website.


Elkhart County Spray Areas                                                                                  


 LaGrange/Noble County Spray Areas



Eastern Equine Encephalitis Virus

Eastern equine encephalitis virus (EEEV) is an arthropod-borne virus (arbovirus) that is primarily transmitted in Indiana by mosquitoes in the genus Coquillettidia. People infected with EEEV can develop severe inflammation in the brain. Only a few cases of EEEV disease are reported in the United States each year. Most occur in eastern or Gulf Coast states.

Eastern equine encephalitis virus. Centers for Disease Control and Prevention.


EEEV can be transmitted in Indiana by mosquitoes in the genus Coquillettidia, but some members of the genus Aedes may also play a role in transmission to humans and animals. These mosquitoes become infected when they feed on infected wild birds. Infected mosquitoes can then spread EEEV to people, horses, and other mammals. Once infected, people and other mammals are “dead-end hosts,” which means that they do not pass the virus on to other biting mosquitoes.  

Signs and Symptoms

Signs and symptoms of EEEV disease usually appear within 4 – 10 days of a bite from an infected mosquito. EEEV infection can result in one of two types of illness, systemic or encephalitic (involving swelling of the brain). It is possible that some people who become infected with EEEV may not develop any symptoms.

Symptoms of systemic EEEV infection appear abruptly and include chills, fever, body aches, and joint pain. People with systemic EEEV infection are usually sick for 1 to 2 weeks and recover completely if the infection does not spread to the central nervous system. In some older children and adults, systemic EEEV infection can progress to encephalitis (inflammation of the brain). In infants, encephalitis can happen abruptly.

Approximately one third of all cases of encephalitis due to EEEV are fatal. Many people who recover will experience severe ongoing complications. People who are younger than 15 years and older than 50 years are at the greatest risk of severe disease if infected with EEE virus. 


Diagnosis of EEEV disease is based on the patient’s signs and symptoms and appropriate laboratory testing. If you think you have EEEV disease, contact your healthcare provider.


No specific medication is available to treat EEEV disease. People with severe illness usually require hospitalization, supportive care, and/or rehabilitation.


The best way to prevent EEEV disease is to avoid mosquito bites. See our mosquito prevention page for more information. 

For more information about Eastern Equine encephalitis virus, visit the CDC EEEV webpage.


While equine cases are occasionally detected, human EEEV disease is rare in Indiana. No cases were reported from 2013–2017. For more information, please visit our annual report pages.

For maps showing recent EEEV infections in people, horses, and mosquitoes, click here.

National statistics for EEEV disease can be found at the CDC EEEV Statistics and Maps webpage.


EEEV Quick Facts

Information for Providers

For EEEV disease diagnosis, treatment, and testing information, click here.


Page Last Updated: October 1, 2019

Page Last Reviewed: July 22, 2019