2 Michigan residents test positive for mosquito-borne Jamestown Canyon virus

A resident of Oakland County and another from Macomb County have tested positive for the Jamestown Canyon virus. They have the first confirmed human cases of mosquito-borne disease in Michigan in 2023, state health officials said.

They may also be the first in the U.S. to contract the virus this year. The U.S. Centers for Disease Control and Prevention reported that, as of July 25, the nation had not yet recorded any confirmed human cases in 2023.

From 2011-22, Michigan had 13 confirmed cases of Jamestown Canyon virus, which is most common in upper Midwestern states of Wisconsin and Minnesota, with infections typically occurring in summer and early fall. The risk is highest in August and September, according to the Michigan Department of Health and Human Services.

“It only takes one bite from an infected mosquito to cause a severe illness, so we advise using insect repellent and wearing long-sleeved shirts and long pants when outdoors during times when mosquitoes are active,” Dr. Natasha Bagdasarian, the state’s chief medical executive, said in a statement. “It’s a good idea to take extra precautions during peak mosquito-biting hours, which are from dusk to dawn.”

What is Jamestown Canyon virus?

Jamestown Canyon virus is one of several types — including West Nile virus and Eastern Equine Encephalitis — that can be spread to people when they are bitten by infected mosquitoes.

The insects contract the viruses after feeding on deer, birds and other animals that carry the viruses in their blood. Mosquitoes then spread the disease to humans and other animals when they bite them.

More:A tiny mosquito bite took away Michigan teen Savanah DeHart’s ability to talk, walk

These viruses cannot be spread by coughing, sneezing or touching an infected person.

So far this year, the CDC reported 69 human cases of West Nile virus nationally, though none have been identified in Michigan. There has been one known human case of Eastern Equine Encephalitis in the U.S. in 2023, reported in Louisiana.

In 2019, the U.S. had a record of 38 known EEE infections. Ten of the cases were from Michigan, and six of those who were infected died.

All four of the Michiganders who survived, including Savanah DeHart, of South Portage, were hospitalized, and three of the four had severe neurological problems, state health officials told the Free Press at the time.

What are the symptoms of Jamestown Canyon virus?

Most people who contract the Jamestown Canyon virus have no symptoms at all. But in those who do, it can cause headache, fever and fatigue. Others can develop symptoms like cough, sore throat and runny nose, according to the CDC. Symptoms typically start between two to 14 days after the bite of an infected mosquito.

In about half of all cases, Jamestown Canyon virus can cause severe illness that affects the brain, such as encephalitis or meningitis, and patients will need hospitalization. Rarely, some people have died from it, the CDC reports.

Symptoms of severe illness from the virus can include:

• High fever
• Stiff neck
• Severe headache
• Muscle weakness
• Confusion
• Loss of coordination
• Difficulty speaking
• Seizures

How is the Jamestown Canyon virus treated?

There are no vaccines to prevent the virus in humans and there is no medication that can treat an infection.

Health officials urge Michiganders to cut the risk of infection by preventing mosquito bites.

What parts of Michigan have infected mosquitoes?

State health officials test mosquito pools throughout the state as part of a Michigan arbovirus surveillance program. They check mosquitoes for Jamestown Canyon virus along with West Nile virus and Eastern Equine Encephalitis to assess the risk of infection in people.

So far this summer, mosquito pools from Bay, Saginaw and Washtenaw counties have tested positive for Jamestown Canyon virus. West Nile virus has been found in mosquitoes in Kalamazoo, Wayne and Washtenaw counties.

The best way to prevent these illnesses is to reduce the number of mosquitoes around your home and avoid mosquito bites, state health officials said. They recommend:

• Eliminating all sources of standing water around your home where mosquitoes can breed, including water in bird baths, old tires and any other object holding water, including abandoned swimming pools and wading pools.
• Making sure doors and windows have tight-fitting screens without tears, gaps or other openings.
• When you are outdoors, using an EPA-registered insect repellent with active ingredients such as DEET, picaridin, IR3535, oil of lemon eucalyptus or para-menthane-diol and 2-undecanone.
• Wearing shoes and socks, light-colored long pants and long-sleeved shirts when outdoors.
• Take extra precautions outdoors when mosquitoes are most active, between dusk and dawn.
• Don’t use insect repellent on infants younger than 2 months old. Instead, dress babies in clothing that covers arms and legs and cover the crib, stroller and baby carrier with mosquito netting.
• Using bed nets when sleeping outdoors or in conditions with no window screens.

Contact Kristen Shamus: [email protected]. Subscribe to the Free Press.