Infected mosquitoes found in Washtenaw County. Officials will monitor

• Another pool of mosquitoes tested positive for James Canyon and West Nile viruses 
• Earlier this month, a sample of the insect tested positive for Eastern equine encephalitis 
• Michigan residents are reminded to used bug spray and other preventative measures to protect themselves and their animals

Michigan health officials in Washtenaw County are encouraging residents to protect themselves against mosquito bites, after another pool of insects recently collected in Washtenaw County tested positive for Jamestown Canyon virus and West Nile virus. 

The mosquitoes were collected in Ann Arbor, Independence Lake County Park in Whitmore Lake, Pinckney Recreation Area and Ypsilanti.

The health officials encourage using insect repellent, wearing light-colored clothes or long sleeve shirts and removing containers that hold water, such as old tires and buckets, to prevent mosquitoes from laying eggs.

Related:

• Michigan health officials find potentially deadly EEE virus in mosquitoes
• Michigan sounds alarm about mosquitoes after Jamestown Canyon virus detected
• Moose herds threatened by ticks, brain worms, the result of climate change

“Unfortunately as we see our climate change a little bit, the influx of some of these illnesses is changing in our area,” said Susan Ringler-Cerniglia, public information officer for the Washtenaw County Health Department. “In the Midwest we haven’t always had some of the mosquito-borne illnesses that we will have in the coming years.” 

People should take precautions against mosquito bites but cases of mosquito-borne diseases are rare and people shouldn’t be too concerned about them, she added.

Both viruses are spread through the bite of infected mosquitoes. Most people who are infected don’t usually have any symptoms according to the U.S. Centers for Disease Control and Prevention. But symptoms, including fever, fatigue, and headache, chills, body aches, joint pain, vomiting, diarrhea, or a rash, can show up in the first four to 10 days after the bite and can last up to two weeks. 

Severe cases, which are rare, can lead to infection of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis), according to the CDC. Less than one percent of people infected with West Nile virus experience encephalitis or meningitis. 

However, people who develop symptoms such as fever, headache, vomiting, diarrhea, seizures, behavioral changes, and drowsiness may be showing signs of a neurological disease.

Though the Jamestown Canyon virus is found across the country, it is most common in the upper Midwest, according to the CDC. Cases of JCV have increased in recent years. In 2022 there was one case reported, six cases in 2021 and three in 2020, the Michigan Department of Health and Human Services confirmed. 

West Nile virus is much more common in the United States and is the leading cause of mosquito-borne disease. In 2022, the virus sickened 12 Michigan residents. 

There were 1,126 reported human cases in the U.S. in 2022 and 90 deaths. 

Mosquitoes are also known to carry diseases like Eastern equine encephalitis (EEE), especially from late spring through mid-fall when they are most active. 

Last month, the Michigan Department of Health and Human Services reported that a pool of mosquitoes in Saginaw County tested positive for Eastern equine encephalitis.

For the past three years, the state has offered virus testing for mosquitoes collected by local health departments and county mosquito control programs. 

“Our mosquito surveillance can help with early detection of infections,” said Kristen Schweighoefer, environmental health director for the Washtenaw County Health Department, in a news release. “We’ll continue to monitor throughout the summer while mosquitoes are active.”