First mosquito-borne virus of 2021 detected in Michigan mosquitoes

Mosquitoes recently collected in Bay, Oakland and Saginaw counties have tested positive for Jamestown Canyon virus (JCV) at the Michigan Department of Health and Human Services Bureau of Laboratories (MDHHS BOL). These are the first infected mosquito pools detected for 2021. Residents are reminded that the best way to protect themselves against JCV and other mosquito-borne illnesses, including Eastern Equine Encephalitis (EEE) and West Nile virus (WNV), is to prevent mosquito bites.
Every summer in Michigan, bites from mosquitoes carry the risk of spreading diseases to people and animals. JCV sickened three Michiganders in 2020. Also reported were 32 cases of WNV and four cases of EEE, resulting in two deaths.
The JCV virus is spread to people through bites from infected mosquitoes. Most cases occur from late spring through mid-fall. Illness can develop within a few days to two weeks following a bite from an infected mosquito. While most people do not become ill, initial symptoms can include fever, headache and fatigue. In rare cases, it can cause severe disease in the brain and/or spinal cord including encephalitis and meningitis.
«It only takes one bite from an infected mosquito to cause a severe illness,» said Dr. Joneigh Khaldun, chief medical executive and chief deputy director for health at MDHHS. «We urge Michiganders to take precautions such as using an EPA-registered insect repellent when outdoors, avoiding areas where mosquitoes are present if possible and wearing clothing to cover arms and legs to prevent bites.»
While the JCV is found throughout much of the U.S., cases have been increasing in the Midwest. This likely reflects increased awareness and testing but may also be due to an increase in the presence of the virus in the environment. This is the first year that the MDHHS BOL is offering virus testing of mosquito pools collected by local health departments and county mosquito control programs. Testing is being offered to improve detection and notification of mosquito-borne viruses.
JCV can be spread by mosquitoes that become infected when they feed on deer or other animals that have the virus in their blood. Infected mosquitoes spread the virus to other animals or people through bites. Arboviruses including WNV and EEE virus spread when mosquitoes contract the virus from biting infected birds then biting a human.
Residents can stay healthy by using simple, effective strategies to protect themselves and their families. The following steps are recommended to avoid JCV and other mosquito-borne diseases:
• Apply insect repellents that contain the active ingredient DEET, or other EPA-approved products to exposed skin or clothing. Always follow the manufacturer’s directions for use.
• 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.
For more information, visit Michigan.gov/EmergingDiseases.