California health officials have reported 28 confirmed deaths so far this year from West Nile virus.
Many of those who died were senior citizens, who health officials said are at a higher risk of getting sick and are more likely to develop complications. Studies indicate that those with diabetes and or hypertension are at greatest risk for serious illness.
As of Friday, 469 people in 30 counties have tested positive for the virus this year, according to the California Department of Health's website. Thirty-three California counties, including Los Angeles, Orange and Ventura, have reported virus activity so far this year, four more than this time last year, and higher than the five-year average of 22.
FOR THE RECORD
Nov. 2, 1 p.m.: An earlier version of this article incorrectly said that 517 people had tested positive for West Nile virus this year.
The related fatalities were reported in the following counties: Butte 1, Kern 1, Los Angeles 8, Nevada 1, Orange 3, Riverside 6, San Bernardino 2, San Diego 5 and Ventura 1.
"West Nile virus activity is more widespread in 2015 than in years past," California Department of Public Health Director Dr. Karen Smith said in a statement earlier this year. "Californians need to be vigilant in protecting themselves."
The virus is transmitted to humans and animals by the bite of an infected mosquito. The risk of serious illness to most people is low. However, some individuals -- less than 1% -- can develop a serious neurological illness such as encephalitis or meningitis.
A record 31 people died in California in 2014 from West Nile virus.
Experts think California's drought may have led to the increased West Nile presence. With fewer sources of water for birds and mosquitoes, they're coming into closer contact with humans in their search for water, increasing the chance of transmission.
Los Angeles County health officials confirmed the death in late September of an elderly Glendale man who'd fallen ill after being bitten by an infected mosquito. Meanwhile, a second Glendale resident is being treated at USC Verdugo Hills Hospital's intensive-care unit after experiencing encephalitis associated with the West Nile virus, the woman's son said last week.
Jennifer Lee, 73, was traveling with relatives to the Grand Canyon on Oct. 21 when she began experiencing fever and tremors, said her son, Paul Mitchell.
Family members took her to the hospital, where she was admitted that day with flu-like symptoms.
"Then it started to evolve to where she was losing a sense of the people around her and getting disoriented," Mitchell said. "By Monday she was unresponsive."
A test revealed Lee carried the antigen identifying the presence of West Nile virus in her body. She has since regained consciousness.
Mitchell said his mother regularly visited a community garden at a nearby residence, but given the incubation period of three to 15 days, it is unknown when or where the mosquito-borne virus was contracted.
Health officials recommend using insect repellent to stave off mosquitoes and wearing protective clothing at dawn and dusk, when the insects are most active. They also recommend emptying vessels such as flower pots or buckets because mosquitoes lay eggs in standing water.
"People over the age of 65 or who have immunosuppressive diseases -- or anyone who doesn't want to get West Nile -- should wear mosquito repellent," advised Laurene Mascola, chief of the Acute Communicable Disease Control Unit of the Los Angeles County Department of Public Health.
"No mosquito is a good mosquito."