Michigan has identified the state’s first two human cases of a mosquito-borne virus in 2023.
A person from Macomb County and a person from Oakland County tested positive for Jamestown Canyon Virus (JCV).
JCV and other mosquito-borne viruses are transmitted through the bite of an infected mosquito. Most people who get the virus have no symptoms of illness, but some become ill two to 14 days after the bite.
Symptoms of JCV include high fever, confusion, muscle weakness, headache, and fatigue. In rare cases, JVC can cause severe disease in the brain and/or spinal cord including encephalitis and meningitis.
There were 10 cases of JVC in Michigan between 2012 and 2021 that were reported to the CDC. According to Michigan, there were 12 JVC-positive mosquito pools in 2022 and one human JCV case.
So far this summer, mosquito pools from Bay, Saginaw, and Washtenaw counties have tested positive for JCV. West Nile Virus has been found in mosquitoes collected in Kalamazoo, Wayne, and Washtenaw counties. The state said the risk for mosquito-borne illness peaks in August and September.
“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,” said Dr. Natasha Bagdasarian, MDHHS chief medical executive “It’s a good idea to take extra precautions during peak mosquito-biting hours, which are from dusk to dawn.”
Preventing mosquito bites
Michigan officials suggest taking the following steps to prevent mosquito bites:
- When used as directed, Environmental Protection Agency (EPA)-registered insect repellents with one of the active ingredients below are proven safe and effective, even for pregnant and breastfeeding women: DEET, Picaridin (known as KBR 3023 and icaridin outside the US), IR3535, Oil of lemon eucalyptus (OLE), Para-menthane-diol (PMD), and 2-undecanone.
- Wear light-colored, 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 lay eggs.
- You could also hire a mosquito control business. Mosquito control businesses are required to be licensed to apply pesticides in Michigan. A list of Michigan firms licensed to apply pesticides is available online.
Mosquitoes lay eggs in or near standing water
Mosquitoes need standing water to reproduce. That’s why you should empty, scrub or cover any items that hold water.
Standing water is often found in old tires, buckets, planters, toys, pools, birdbaths, flower pot saucers or trash containers.
Mosquitoes can complete their life cycle in about a week. The CDC recommends using an outdoor insect spray made to kill adult mosquitoes. Mosquitoes are often found in dark, humid areas.
Can’t remove standing water? Larvicides are an option
If you’re unable to remove the standing water where you live then you’ve got one other option: Larvicides.
Larvicides work by killing mosquito larvae and pupae before they grow into pesky adults. According to the CDC, if you use larvicides correctly they do not harm people, pets or the environment.
Larvicides come in liquids, tablets, bits, pellets, granules and briquettes. You use them by applying them where mosquitoes lay eggs (that means anywhere that holds standing water). That can include buckets and rain barrels, fountains, gutters or downspouts, non-chlorinated swimming pools, pool covers that collect water, tires and tree holes.
Use larvicides to treat standing water that will not be used for drinking and cannot be covered, dumped or removed.
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