CONTRA COSTA COUNTY (KRON) — A group of mosquitos and three more dead birds have tested positive for the West Niles virus in Contra Costa County, Mosquito & Vector Control District officials said.

Officials found one infected bird in Concord, and another in Martinez, and a third in Walnut Creek, while the mosquitoes were trapped near Knightsen.

In 2016, nine mosquito samples and 25 birds have tested positive for the virus, officials said.

Vector control officials are emphasizing that even though it’s fall, mosquitoes are still active and residents should protect themselves as warm weather lingers.

“People still need to protect themselves until the cooler weather arrives and the mosquitoes go to sleep for the winter,” district scientific program manager Steve Schultz said in a statement.

Vector control officials suggest reducing the risk of getting bit by dumping or draining standing water, using repellents containing DEET, oil of lemon eucalyptus or Picaridin and staying indoors, especially at dawn and dusk.

Maintaining swimming pools is especially important since one pool can breed more than 1 million mosquitoes and affect people up to 5 miles away.

Residents can review this year’s activity among birds and mosquitoes in the county by going to For information about human cases, residents can call (888) 959-9911.Vector control officials urge residents to report dead birds to the state’s hotline at (877) 968-2473 or at City News contributed to this report.