(CBS) — A batch of mosquitos in Skokie has tested positive for the West Nile Virus, making it the fourth Chicago suburb to detect the disease this year.

The potentially deadly virus was first discovered in Oak Lawn and Evergreen Park in May. Then it was found in Evanston, and now Skokie.

So far no human cases of the virus have been reported this year.

Local health departments have been working diligently to kill mosquitos, which carry the disease, and warn people of the dangers.

Symptoms generally don’t appear for 3 to 14 days after a person has been bitten by an infected mosquito. Anyone can get West Nile Virus, but typically people over 50 years of age and individuals with weakened immune systems are most likely to develop severe illness.

Residents in the affected suburbs are concerned.

“It scares me a little bit, because the mosquitos are really bad, and I’ve got three grandkids that I’ve got to worry about,” Skokie resident Joe Putnick said.

Officials were warning local residents to protect themselves by avoiding outdoor activities at dusk and dawn, when mosquitos are most active. You should also wear long sleeves and pants, and use insect repellant.

“I’ve just been putting bug spray on my hands, and wiping it on [my daughter] just to make sure that she doesn’t get it,” said concerned mother Tricia Migely.

Homeowners should also empty anything around their homes containing standing water, which creates the perfect breeding ground for mosquitoes.