SACRAMENTO, Calif. -- Aerial spraying may be necessary this summer to help combat the spread of West Nile virus in the region, the Sacramento-Yolo Mosquito and Vector Control District said Tuesday.

"We're very concerned about the increased activity in this area and we are evaluating our response," district manager David Brown said in a statement. "Though no formal decisions have been made, it may be necessary as early as next week to begin aerial treatments to reduce the mosquito population and risk of West Nile virus transmission."

Brown said residents should protect themselves by wearing repellent.

District officials warn about creating more mosquitoes in yards by leaving out standing pools of water.

Pool-related cases handled by the vector control district for Sacramento and Yolo counties have increased sixfold in the first half of 2008 compared to the same period last year.

Technicians made 3,000 pool-related visits from January to June.

Many of the pools are in homes that have been repossessed by lenders.

A house finch and a crow found in the Pocket and Oak Park areas tested positive for the virus last month, and a dead bird was also found in the Antelope area.

The first human case of West Nile virus in 2008 was confirmed in Tulare County.