ST. LOUIS (KMOX) – Expected heavy rains this weekend, thanks to Hurricane Isaac, have prompted St. Louis County health officials to step up their spraying efforts to knock down the mosquito threat.

No human West Nile virus cases have arrived here yet but St. Louis County health officials say they’re seeing a greater abundance of West Nile in the mosquito populations they’re able to test.

Drew Hane is the Vector Control Supervisor for St. Louis County.

“We’re at about nine percent for the month of August which is up from the four or five percent we usually see,” Hane said.

Hane says residents also should make a special effort to drain any standing water from around the home to eliminate mosquito breeding grounds.