A 49-year-old woman from Spring Valley is the first in San Diego County this year to be infected with West Nile virus, according to the county Health and Human Services Agency.
West Nile cases have dropped precipitously since 2016 when 22 cases and two deaths were reported.
Dr. Eric McDonald, chief of the county’s Epidemiology and Immunization Services Branch, said the woman’s infection caused a less-severe version of the disease that results in headache, body aches, joint aches, joint pains, vomiting, diarrhea or rash, according to the U.S. Centers for Disease Control and Prevention.
“She was able to fully recover and she wasn’t hospitalized,” McDonald said.
A horse in Escondido also tested positive for West Nile, one of 17 infected across the state, according to the latest update from the California Department of Public Health.
About one in five people have the fever version of the disease. In one case out of every 150, serious neurological symptoms develop, causing inflammation of the brain and/or the membranes that surround the brain and spinal cord. Inflammation can cause coma, tremors, convulsions, vision loss and paralysis. One in 10 patients with central nervous system symptoms die.
McDonald said it is unclear why San Diego has seen so few West Nile infections so far this year. That has not been the case, he noted, in other parts of Southern California.
“Normally we start having cases show up in August when mosquito season starts. That has certainly been the case in Los Angeles this year,” McDonald said.
According to the state health department, there have been 258 West Nile cases in California this year with 121 in Los Angeles County which saw six of the state’s 12 West-Nile-related deaths.
Birds are the virus’s natural reservoir. Mosquitoes that feed on birds and humans can pass the infection. There is a vaccine that can prevent infection in horses but not humans.