San Diego County health officials are on alert after a dead crow found in North Park tested positive for West Nile virus — the first confirmed detection of the mosquito-borne illness in the county this year, according to county environmental health officials.

The virus is primarily a bird disease, but it can be transmitted to humans when certain types of mosquitoes feed on an infected bird and then bite a person. While no human cases have been reported this year, health officials are treating the detection seriously given the county's history with the disease. In 2015, 44 San Diego County residents tested positive for West Nile virus and six died.

Warmer weather allows mosquito season to start earlier than usual, compounding the concern. San Diego County's Vector Control Program is responding by increasing surveillance and treating mosquito breeding sources at approximately 1,600 identified sites countywide. Larvicide is being applied by air, boat, truck, and hand crews.

Residents across East County can help reduce the risk by dumping out standing water in plant saucers, rain barrels, buckets, garbage cans, toys, old tires, and wheelbarrows — common breeding grounds for mosquitoes. The Vector Control Program is also offering free mosquito fish that can be placed in stagnant water to naturally control mosquito breeding.

Anyone who spends time outdoors — including hikers, campers, and those working in the yard — should wear long sleeves and pants and apply insect repellent. Mosquito activity or breeding sources can be reported to the Vector Control Program by calling 858-694-2888 or emailing vector@sdcounty.ca.gov.