SAN DIEGO - County health officials Wednesday reported the first human case of West Nile virus in the San Diego region this year, involving a 51-year-old El Cajon woman who was sickened but not hospitalized.
The woman donated blood on July 27 and was found to have evidence of active infection. She subsequently developed symptoms of fever and headache and was diagnosed with WNV, county officials reported.
Blood donations in the United States are screened for the mosquito-borne virus and other diseases that can be transmitted in a transfusion.
County Department of Environmental Health Vector Control Program staff members are conducting inspections near the woman's home to check for potential sources of mosquito breeding. Vector Control also set up traps in the area and is sending notifications to residents.
More dead birds and batches of mosquitoes infected with the virus have been discovered this year than in recent years. Mosquitoes can transmit West Nile virus to people by feeding on infected birds and then biting humans.
Environmental Health officials identified 185 dead birds and 77 batches of mosquitoes that tested positive for West Nile virus to date. At this point last year, the county had collected a total of 69 dead birds and 14 mosquito batches that tested positive for the virus.
Last year was also the deadliest year ever in San Diego for WNV, with six deaths among the 44 human cases reported.
"The numbers of dead birds and positive mosquito batches positive for West Nile virus has increased from what was found last year, so it's important for the public to know the facts about how to prevent mosquito breeding and protect against mosquito bites," said Dr. Wilma Wooten, the county's public health officer.
The San Diego County report came on the same day that health officials in neighboring Orange County announced their first human WNV case. The first infected person in Los Angeles County was reported late last month.
The best protection against WNV is to empty out areas of standing water where mosquitoes breed, stay indoors at dusk and dawn when the insects are most active, and wear long sleeves and pants or use repellent when outdoors.
About 80 percent of people with WNV don't get symptoms, while the remainder will have headaches, fever, nausea, fatigue, a skin rash or swollen glands.
An estimated one in 150 cases are life-threatening, with the risk going up for patients over age 50, according to the county Health and Human Services Agency.
County officials also urged residents to contact vector control when they find dead birds or green swimming pools, by calling (858) 694-2888 or emailing email@example.com.