GRAND RAPIDS, Mich. (WOOD) — Several Kent County residents have tested positive for West Nile virus, according to the county health department.

The agency says tests confirmed the virus was present in four people; a fifth resident is also suspected of having the illness.

It’s unclear if any of those sickened were hospitalized.

Health officials say they’re not sure where the residents contracted the mosquito borne virus, but they’re concerned more people may be at risk with the unseasonably warm weekend weather.

“People need to know that mosquitoes are still quite active this time of year,” stated health officer Adam London in a Friday news release.

If you’re going outside, health officials advise you wear light-colored clothing, mosquito repellent that contains 10-35 percent DEET, and come inside at dusk.

A Kent County pool of mosquitoes first tested positive for West Nile virus in August.

State health officials say West Nile virus activity this year appears to be widespread across Michigan. Two people from Montcalm County were among the first four Michigan residents confirmed to have West Nile virus this year, according to the Michigan Department of Health and Human Services.

While most people sickened by West Nile virus do not develop any symptoms, health officials say about 20 percent suffer mild illness with fever and about 1 in 150 people become severely ill.

Mild symptoms may include headache, body aches, joint pain, vomiting, diarrhea, or rash. Severe symptoms of West Nile virus are associated with encephalitis or meningitis, and may include stiff neck, stupor, disorientation, coma, tremors, muscle weakness, convulsions and paralysis.