The latest confirmed victim, a Long Beach woman whose name wasn't released, died Monday after spending nearly two weeks in the hospital, said Dr. Darryl Sexton, the city's health officer.
Her case marked the first confirmed death in Los Angeles County. The state's two other confirmed West Nile deaths were in San Bernardino and Orange counties.
A spokeswoman from Kaiser Permanente hospital in Panorama City said preliminary tests showed a 91-year-old woman also died of the virus last week. Officials will conduct another blood test to confirm the results.
West Nile, which first hit the United States in 1999 in New York, has killed more than 560 people in the past five years as it marched westward. Last year was the first for the virus to appear in areas west of the Continental Divide.