A 72-year-old Buena Park woman became the first person in California to die from the West Nile virus infection this year, the Orange County Health Care Agency reported Monday.
Testing confirmed that the woman died from complications from West Nile neuroinvasive disease, the more serious neurological form of the disease, said Howard Sutter, spokesman for the Orange County Health Care Agency. She died this month, but healthcare officials would not provide a specific date or say where she had been hospitalized.
This is the first West Nile-related fatality in Orange County since 2004. There have been 30 cases of West Nile reported in 2008 in the county, a higher number than usual for this time of year, Sutter said.
Four of the Orange County residents did not exhibit symptoms of the disease even though tests showed they had been infected.
The woman was probably infected by a mosquito, Sutter said. Humans and animals contract the West Nile virus from the bites of infected mosquitoes, which contract it by feeding on birds that have the virus in their blood.
Health officials say the risk of human infection in Southern California is the highest it has been since 2004, when 710 people became infected with the virus and 21 died.
"We think it is very important that people take the precautions they can take to protect themselves against mosquito bites," Sutter said. "This is an important reminder that this can be a serious illness. It is a very unpredictable virus."
As of Monday, 112 cases of human West Nile virus have been confirmed in the state, with 97 of the infected people showing symptoms. The peak season for infections is between August and October, and the Southern California region has seen an increased number of dead birds and mosquitoes this year, officials said.
Officials have blamed much of the increase in the virus on the thousands of abandoned swimming pools in foreclosed homes throughout Southern California, which provide a breeding ground for mosquitoes.
The neurological form of the virus, which the Buena Park woman died from, is on the rise this year, Sutter said. Though it usually affects people older than 50, it has infected 21 of the 30 Orange County individuals infected with West Nile this year, said Deanne Thompson, a health agency spokeswoman. Scientists and healthcare officials do not know why there have been more cases of the neurological form this year, she said.
Most people who are infected by the virus do not become ill, but about 20% develop flu-like symptoms. In its most severe form, West Nile can cause encephalitis, meningitis and death.
Officials recommend that people use insect repellent, put screens on their windows, get rid of standing water and wear long pants and long-sleeved shirts at dawn and dusk, when mosquitoes are most active.