Sacramento County is reporting California's first human death in 2013 from West Nile virus, a disease spread by bites from infected mosquitoes.
The Sacramento County man tested positive for the virus earlier this year, the state Department of Public Health said.
"His illness, as well as his laboratory test results, are potentially consistent with West Nile neuroinvasive disease," the department reported on its website, westnile.ca.gov.
No other county has reported any human cases, whether infected or deceased. The Sacramento County victim's identity is not being released because of health privacy laws.
But the agency known for its "Fight the Bite" campaign reported last week that it has detected the first signs of West Nile virus in dead birds and mosquito samples in the Sacramento region.
Two dead birds, plus two mosquito samples, were found to be carriers of the disease at the Sacramento County Public Health Laboratory, according to the Sacramento-Yolo Mosquito and Vector Control District.
Other counties Merced, Los Angeles, Fresno, Orange, Ventura and Yuba already had reported the presence of the virus in a total of 10 dead birds.
In Sacramento County, the birds and mosquitoes were collected over a widespread area, so there's no reason to worry that a particular neighborhood is at risk, officials said.
"Finding the first positive birds is always significant because it provides an early warning sign for the disease," said District Manager David Brown.
At this point, the district does not have plans to immediately begin targeted spraying of pesticides within neighborhood areas.
Symptoms of the virus, caused by a bite from an infected mosquito, include fever, headaches, neck stiffness and body aches.
In severe cases, the virus may lead to stupor, coma, tremors, convulsions, muscle weakness and paralysis. The worst cases can lead to hospitalization from encephalitis, or inflammation of the brain, as was the case with the Sacramento victim.
While it has been known that the disease may contribute to long-term nerve and brain damage, researchers have begun looking into whether West Nile virus may also damage the kidneys.
Fortunately, most people infected with the virus will have no symptoms, according to the federal Centers for Disease Control and Prevention.
About one in five people with the virus develops a fever with other symptoms, the CDC said. Less than 1 percent of infected people develop serious, sometimes fatal, neurologic illness.
Last year, California saw 479 human West Nile virus cases, with 20 deaths.
For those concerned about pesticides that will be used to combat the virus' spread, the Sacramento-Yolo district is allowing residents to be notified of targeted applications anywhere in the two-county region. Forms can be filled out at www.fightthebite.net.
Previously, residents could ask to be notified of pesticide applications only in a single, designated ZIP code.