Yolo County reports first West Nile virus death since 2018 as ‘bad mosquito’ year continues

Health officials on Thursday announced the first West Nile virus death this year in Yolo County, the county’s first reported human fatality from the mosquito-borne disease in five years.

The Yolo County resident who died succumbed to the infection after experiencing symptoms consistent with neuroinvasive West Nile virus disease, according to a news release. County officials did not release any further details about the person who died.

The death is the first from West Nile virus in the county since 2018. The county already has recorded more human West Nile virus cases than it did last year, according to Thursday’s news release. Public health officials have identified eight cases of West Nile virus among Yolo County residents to date in 2023, compared to three total human cases last year.

Health officials said they have seen cases of severe neuroinvasive disease in younger people this season, which shows “the need to take West Nile virus prevention seriously regardless of your age.”

“This tragic death underscores the importance of preventing mosquito bites,” Yolo County Public Health Officer Dr. Aimee Sisson said in the news release. “While most West Nile virus infections have no symptoms, some people get very sick and may die, especially older adults and people with underlying conditions or weakened immune systems.”

The Yolo County death was reported one day after health officials announced the first reported West Nile virus death this year in Sacramento County. The person who died was in their 70s, had underlying chronic disease and had been hospitalized with neuroinvasive West Nile virus.

West Nile virus is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds.

Health officials said symptoms usually develop within a week after being bit by an infected mosquito. West Nile virus symptoms may include fever, nausea, headaches, and muscle aches, lasting from a few days to several weeks. While most people infected have no symptoms, severe complications such as meningitis, encephalitis, paralysis or even death can occur, particularly in those older than 60 years old or with compromised immune systems.

Sisson said 2023 has been “a bad mosquito and West Nile virus year.” One in four mosquito samples in the county is testing positive for West Nile virus. The health officer urged residents to protect themselves and their loved ones from mosquito bites, especially around dawn and dusk when mosquitoes are most active.

As of last Friday, officials had confirmed 26 human cases of West Nile virus in California this year. In 2022, there were 207 human cases detected in the state, according to the California Department of Public Health.

The Sacramento-Yolo Mosquito and Vector Control District has been monitoring the mosquito population on the ground, identifying areas with West Nile virus detected in bird and mosquito samples. District officials said test results last week confirmed 83 mosquito samples tested positive, a sharp increase especially in Davis and Woodland, where much of the West Nile virus activity is concentrated.

The district has been using planes this summer to spray aerial treatments to reduce the mosquito population in those areas.

“It has been a very intense season for West Nile virus, and the risk of becoming sick is very real,” Sacramento-Yolo Mosquito and Vector Control District manager Gary Goodman said in Thursday’s news release.

The district warned residents on Monday about the spread of West Nile virus as activity remained “intense and widespread throughout Sacramento and Yolo counties.”

“We are very concerned about the intense activity, especially since we are still in the middle of the summer and typically we don’t see a decrease in mosquitoes until mid-September,” Goodman warned Monday.

Authorities with the local district offered these tips to reduce mosquito exposure:

▪ Drain any stagnant water to eliminate mosquito breeding sites.

▪ Dawn and dusk, when mosquitoes are most active, are times to limit outdoor activities.

▪ Dress in long sleeves and pants when outdoors.

▪ Defend against mosquitoes by using effective insect repellents containing DEET, Picaridin, or Oil ofLemon Eucalyptus.

▪ Make sure door and window screens are intact to prevent mosquitoes from entering homes.

▪ For assistance, call the Sacramento-Yolo Mosquito & Vector Control District at 1-800-429-1022 to address mosquito concerns.