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Posted on: September 18, 2019

Eastern Equine Encephalitis

EEE web

BCHD News Releases Regarding Eastern Equine Encephalitis

News Release: September 18th, 2019


Frequently Asked Questions

What is Eastern equine encephalitis (EEE)?
EEE is a rare disease that is caused by a virus spread by infected mosquitoes. EEE is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain (encephalitis). 

How do people get infected with EEE?
EEE is only transmitted through the bite of an infected mosquito. Disease transmission does not occur directly from person to person and the virus cannot be spread by an animal, like a horse or deer, to a human.

How many cases of EEE have been in Michigan?
As of September 27th, 2019, there have been nine (9) confirmed human cases of EEE in Michigan. In Berrien County, there has been two (2) confirmed human cases. Updated case counts can be found at the Michigan Department of Health and Human Services website.

Who is most at-risk for EEE infection?
Individual cases of EEE are more likely to occur in those over the age of 50, under the age of 15, or those who may have weakened immune systems from underlying medical conditions or treatments. Only about 4-5% of human infections result in EEE illness.

How soon do people get sick after getting bitten by an infected mosquito?
It takes 4 to 10 days after the bite of an infected mosquito to develop symptoms of EEE.

What are the symptoms?
Severe cases of EEE infection begin with the sudden onset of headache, high fever, chills, and vomiting. The illness may then progress into disorientation, seizures, and coma. Approximately a third of patients who develop EEE die, and many of those who survive have mild to severe brain damage. 

Do all mosquitoes spread EEE?
Not all mosquitoes carry the EEE virus; the species of mosquito that can carry and spread the virus are most often found in and around hardwood forests or freshwater swamps/bogs. These mosquitoes are most active at nighttime, between dusk and dawn. 

How can I prevent EEE and mosquito bites?

  • When outdoors, apply insect repellents that contain the active ingredient DEET, or other U.S. Environmental Protection Agency-registered product to exposed skin or clothing, and always follow the manufacturer’s directions for use.
  • Wear long-sleeved shirts and long pants when outdoors. Apply insect repellent to clothing to help prevent bites.
  • Maintain window and door screening to help keep mosquitoes outside.
  • Empty water from mosquito breeding sites around the home, such as buckets, unused kiddie pools old tires or similar sites where mosquitoes may lay eggs.
  • Find other mosquito bite prevention information here.

What is aerial spraying and why is it happening now?
There has been a record number of cases of Eastern Equine Encephalitis (EEE) this year. Given the elevated risk of human illness due to this virus that is spread by mosquitoes, your state and local health officials are opting to use an aerial insecticide to reduce the number of potentially infected, adult mosquitoes in the specific areas of elevated risk.

How and when will aerial spraying happen? 
Updated 10/2/19: Aerial spraying was completed for the portions of Berrien County as planned on the evening of October 1, 2019. The portions of the county that were sprayed includes areas in Pipestone Township, Berrien Township, and the Village of Eau Claire. Berrien County EEE Aerial Spray Zone Boundaries_lands-1

Aerial spraying is conducted by airplane that flies over the areas of concern during early evening and nighttime hours (approximately 8PM-4AM), weather permitting, to distribute the insecticide product. Please find more information about aerial spraying here. Mosquito control professionals apply approved insecticide as an ultra low volume (ULV) spray. ULV sprayers dispense very fine aerosol droplets (about 1 ounce per acre or about the size of a football field) that kill adult mosquitoes on contact in the air. See this map for the specific areas that will be impacted by aerial spraying. Note: the map does not reflect areas that have "opted out" of aerial spraying. 

Is aerial spraying of insecticides dangerous/harmful to human health?
No, during aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre or about the size of a football field. This small amount does not pose a health risk to people or pets in the area that is sprayed. The insecticide being used, Merus 3.0, is an EPA-registered, organic product developed for aerial spraying that is conducted by a licensed professional. If people prefer to stay inside and close windows and doors when spraying takes place they can, but it is not necessary.

How effective is aerial spraying? Do I still need to wear insect repellent?
Aerial spraying is extremely effective to eliminate up to 90% of the adult mosquito population in the area where insecticide is applied. However, it is recommended that you still take precautions to prevent mosquito bites by wearing an EPA-approved insect repellent, long sleeves/pants, and consider limiting time outdoors between dusk and dawn.

What can I do if I am concerned about the mosquito spraying that is happening?
In general, no special actions are needed before or after the aerial spraying occurs. If you wish to take extra precautions, you may choose to:

  • Remain inside during the hours that spraying occurs
  • Close windows and doors. Turn off air conditioners and window fans that bring outdoor air inside.
  • Bring outdoor items (laundry, outdoor furniture, children's toys) inside or cover them, if possible.
  • Keep pets/animals indoors and cover swimming pools.

Can residents opt out of the aerial spraying? 
We are currently in a public health emergency and aerial applications provide the most effective option to suppress the outbreak by reducing mosquito populations.  Due to the height and speed the plane will operate, it is not possible to stop the spraying over a single property. If an individual wishes to opt out of the application, under MDARD rules, an area of 1,000 x 1,000 feet would not be sprayed around the residence.  This will reduce the overall treatment effectiveness in the area, mosquito populations upwind of the opt-out area will not be reduced, and neighbors will not benefit from the reduction in mosquito numbers.  

Before exercising this option, please recall that EEE is highly deadly, and that this aerial spraying does not carry any significant risks to human health. While it is unnecessary to do so, you can further reduce your exposure by staying indoors, and closing windows and doors. If, for whatever reason, you would still prefer that spraying not occur in your area, you may send an email with your name and full residential address to eee@michigan.gov.  The request to opt out of spraying must be received at least 48 hours before spraying begins.


Additional Resources & Links

BCHD: Get The Facts on EEE - Prevent Mosquito Bites (PDF) Factsheet
BCHD: Agarre los hechos y datos de EEE – Protegerse de Las Mordeduras de Zancudos
BCHD: Factsheet on Aerial Spraying for Mosquitoes
MDHHS: Frequently Asked Questions about EEE & Aerial Spraying

Map of Portions of Berrien County that will be sprayed for mosquitoes (note: map does not reflect areas that have opted out)
Aerial Spraying Schedule

Website: Centers for Disease Control and Prevention
Website: Michigan Department of Health and Human Services
Michigan Department of Health & Human Services Phone Number: (517) 335-81

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