Toronto Public Health officials began their annual routine of tracking the West Nile virus on Monday.

Officials donned their safety gear and dropped large tablets of larvacide into catch basins and storm drains at key areas around the city, marking each spot with a red spray-painted dot.

The exercise is repeated three times throughout the summer, in order to track whether mosquitoes carrying the West Nile virus are a threat to city residents.

The program began in 2003 after ll people died from the virus the year before.

"Last year was a very good year for us in terms of cases," said Danny Kartzalis with Toronto Public Health. "There were four reported cases and two were travel related."

Kartzalis told CTV Toronto that the long winter the city endured has helped delay mosquitoes as the bugs tend to thrive in warm, dry conditions.

However, with the hot weather the city has been experiencing, officials say it's time to start tracking and eliminating the potential for the dangerous disease.

Aside from dropping larvacide tablets, health officials have also installed traps at 43 locations across the city. Bugs that are caught in the traps are taken to a special lab for examination. The tests help officials determine whether West Nile is present.

The entire program, which includes larvaciding and public education, costs the city about $2.5 million.

Residents are being asked to look around their properties and get rid of any standing water.

With a report from CTV Toronto's Galit Solomon