A mosquito is shown.
Health officials urge people to take extra precautions near dusk and dawn to avoid mosquito bites. (For Spectrum Health Beat)

An outbreak of a mosquito-borne disease raises alarm—and lots of questions—for those who live in the affected area of Southwest Michigan.

How worried should they be about Eastern equine encephalitis? And how can they protect themselves from it?

Julie Kehdi, DO, an infectious disease specialist for Spectrum Health, discussed the risks involved in the outbreak, which state health officials call the worst in a decade.

“In the last decade, there have been seven cases (of Eastern equine encephalitis) in Michigan,” Dr. Kehdi said. “This year alone, we have had seven cases. We have had a dramatic increase.”

Eastern equine encephalitis is a disease, transmitted by mosquito bites, that affects horses and deer, as well as humans.

Most people exposed to the virus through a mosquito bite never become ill.

“Ninety-five to 96 percent won’t have any significant disease,” Dr. Kehdi said. “A very small subset will actually have clinical disease.”

Some will develop systemic illness, which involves flu-like symptoms such as a fever, headaches and achiness. It typically clears up in a week or two.

About 4 to 5 percent of those exposed to the virus may develop a more severe illness, called encephalitis, which can cause disorientation, tremors, seizures and paralysis.

The Michigan Department of Health and Human Services encourages anyone experiencing symptoms of Eastern equine encephalitis to visit their physician’s office.

The severe form of the disease causes swelling on the brain, with damage to the central nervous system, Dr. Kehdi said.

“It’s a very damaging type of infection,” she said. “One of the troubling aspects is that there is nothing we can do to reverse it once it sets in.”

Medical treatment focuses on supportive measures, such as medication for fevers or ventilator support for breathing.

The severe form of the disease has a 33 percent fatality rate. Those who survive may suffer permanent brain damage.

The people at greatest risk of developing it are those under age 15 and over 50.

“Any type of weakened immune system is going to make you more vulnerable to infections,” Dr. Kehdi said. “That’s why the ends of the age spectrum tend to be more vulnerable.”

Prevention is key

The first hard frost eventually will take care of the problem for the season by killing mosquitoes. Until then, Dr. Kehdi says residents should protect themselves by avoiding mosquito bites.

Her tips include:

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Mosquito bite prevention. How to avoid mosquito bites and how to keep your house safe. (For Spectrum Health Beat)
  • Stay inside at dusk and in the evening.
  • If going outdoors, wear long sleeves and long pants, and use insect repellant.
  • Empty containers with standing water, which can be breeding grounds for mosquitoes.
  • If you crack windows indoors, make sure there are screens to keep out the insects.

The state health department reported this week that seven cases of Eastern equine encephalitis were reported in five Southwest Michigan counties: Barry, Berrien, Cass, Kalamazoo and Van Buren. Three people died from the disease.

Nine cases of the disease were reported in horses in Barry, St. Joseph, Genesee and Lapeer counties.

The health department encourages officials in all eight counties to consider postponing or canceling outdoor activities at dusk or later in the evening, particularly those that involve children.

The recommendation “is being made out of an abundance of caution to protect the public health and applies until the first hard frost of the year,” health officials said.