There's more evidence of the presence of West Nile virus in Sarnia-Lambton.
Lambton Public Health Supervisor Lori Lucas says mosquitoes collected August 1 from a trap in Wyoming have tested positive for the virus.
This is the second positive finding as part of West Nile virus surveillance this summer.
A crow tested positive in Sarnia in late July.
No human cases of West Nile virus have been reported.
Residents are again urged to take precautions to prevent exposure to mosquitoes by eliminating breeding sites and standing water and wearing insect repellent containing DEET.
West Nile virus is spread to humans through the bite of an infected mosquito. However, the majority of people infected with the virus do not get sick.
Those that do, usually experience mild flu-like symptoms like fever, headache, skin rash or muscle aches.
Less than 1% of people infected with the virus get seriously ill.