Health officials to use aerial spray for mosquito-borne virus EEE

The Michigan Department of Health and Human Services has decided to spray pesticides in several counties in efforts to combat Eastern equine encephalitis (EEE).

EEE is a mosquito-borne virus that has been the confirmed cause of death for three people in southwestern Michigan and for several animals, including two wolf pups at the zoo in Battle Creek. 

The warm weather forecast is one of the factors that led officials to use the spray, as the virus remains a threat until the first hard frost.


The spraying will take place on Sunday, Sept. 29 beginning at 8 p.m., weather depending. 

Spraying will occur in the following 14 counties: Allegan, Barry, Berrien, Branch, Calhoun, Cass, Jackson, Kalamazoo, Kent, Lapeer, Montcalm, Newaygo, St. Joseph and Van Buren. All of these counties have cases of EEE in people, animals or both. 

You may see a low-flying aircraft that evening and overnight in the areas of concern. The plane will be spraying an approved pesticide that will stay suspended in the air and kill adult mosquitoes on contact. 

Other states such as Massachusetts and Rhode Island have recently also used this spray to combat EEE.


The pesticide being used is Merus 3.0 which is an organic pesticide containing 5 percent pyrethrin. Pyrethrins are chemicals found naturally in some chrysanthemum flowers. They are a mixture of six chemicals that are toxic to insects. Pyrethrins are commonly used to control mosquitoes, fleas, flies, moths, ants and many other pests. Pyrethrins have been registered for use in pesticides since the 1950s.

In general, health risks are not expected during or after spraying. No special precautions are recommended; however, residents and individuals who have known sensitivities to pyrethrins can reduce the potential for exposure by staying indoors during spraying. 

Aerial spraying is not expected to have any impacts on surface water or drinking water.

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Aerial spraying will be conducted in the nighttime hours as this is when mosquitos are more active. It is also when fish are less likely to be at the surface feeding and honeybees are most likely to be in their hives. However, owners should cover small ornamental fishponds during the night of spraying. While it is not necessary to bring animals indoors during spraying, concerned pet owners can bring animals inside during spraying.


EEE has a 33 percent fatality rate for those who become sick from the disease. For kids under 15 years old and adults over the age of 50, the fatality rate can rise as high as 50 percent.

Symptoms exhibited by the disease aren't very obvious. Of the 4 to 5 percent of people who do contract the disease and show symptoms, they include chills, fever, weakness, muscle and joint pain and can last up to two weeks. However, for the 1 percent of people who do show serious symptoms, they include neurologic issues like inflammation of the brain.

EEE is typically a serious problem for horses, which is why a vaccine was developed if they contract the disease. No vaccine exists for humans.

People are urged to guard against mosquito bites. The department is encouraging officials in affected counties to consider postponing, rescheduling or canceling outdoor activities including sports occurring at or after dusk until there's a hard frost. 

The projection of warm weather is one of the factors that led MDHHS to make the decision to spray. 

You can learn more about EEE in the State of Michigan here

Fox 2 reported on this story from Southfield, Mich.