The Simcoe Muskoka Health Care Unit is warning residents to layer on the bug spray.
Officials with the unit have confirmed a mosquito pool in Barrie has tested positive for West Nile virus.
Residents in the area should take precautions when outside by using approved mosquito repellent, getting rid of standing water around your home and staying indoors during dusk and dawn.
Be aware of the symptoms that come with West Nile like fever, confusion, a sudden sensitivity to light and muscle weakness.
If you are feeling a combination of these symptoms you should talk to your doctor or a medical professional right away.
Officials say most people will not become sick if bitten by an infected mosquito.