Public Health Madison and Dane County said on Wednesday there's been a spike in reports of dead birds throughout Dane County, and high mosquito activity.
However, the health unit confirms the virus was found in mosquitoes located within a trap in Bradford West Gwillimbury.
Health officials are looking into two potential human cases of the West Nile virus in Simcoe County.
"Because mosquitoes lay their eggs in standing water, public health asks property owners to remove standing water anywhere it tends to collect", stated a WDGPH press release.
About 80% of people who get the virus don't know they have it.
"Everything does clear up, but it's not a fun illness to have".
The best way for people to protect themselves against West Nile is to minimize their risk of mosquito bites by doing things like wearing light-coloured clothing and long-sleeved shirts, and using mosquito repellents containing DEET or icaridin.
The virus causes flu-like symptoms in humans, but in rare cases, inflammation of the brain and spinal column can cause permanent disability or death.
An adult mosquito is shown in the laboratory at the Middlesex-London Health Unit in Strathroy.
It is not uncommon for this part of southern Ontario to see a low number of human cases of the disease per year.