West Nile virus blamed in death of Fresno man, the second in the state this year

A mosquito trapped in 2004 by Los Angeles County Vector Control officers.
(Bob Chamberlin / Los Angeles Times)

A Fresno man has died of West Nile virus, the second person killed in the state by the disease this year, officials say.

West Nile virus, which is transmitted to humans through a mosquito bite, kills several Californians every year. Health officials announced the first victim of 2019 last month, a 74-year-old man in Imperial County.

Fresno County health officials did not provide information about the person who died. He was identified by the Fresno Bee as Robert Diaz, 78.


Of those who contract West Nile virus, only one in five have any symptoms. But one in 150 who are infected develop a serious illness that can be fatal, according to the U.S. Centers for Disease Control and Prevention. Though serious illness can occur in people of any age, it is most likely to affect people over 50.

Last year, 11 people in California died of West Nile, while 44 people were killed the previous year. Los Angeles County officials announced earlier this month that two people were sick with West Nile virus but were recovering.

On Friday morning, officials from the Greater Los Angeles Vector Control District announced additional cities and neighborhoods where mosquitoes with West Nile have been detected. Among them are Long Beach, Cerritos and Northridge.

Health officials recommend that people protect themselves from West Nile by applying bug repellent, clearing their yards of standing water that attracts insects and wearing long sleeves and pants at dawn and dusk, when mosquitoes are most active.

West Nile virus was first detected in Uganda and reached California’s Imperial Valley in 2003.

Since then, nearly 7,000 Californians have been diagnosed with West Nile and more than 300 have died from the illness, according to state data. The virus has become the most prevalent mosquito-borne disease in the United States.


Health experts say that warm temperatures make it more likely for mosquitoes to breed and infect humans with the virus. This year in particular, late spring rains left standing water, where mosquitoes breed.

To monitor West Nile levels across the state, health workers test mosquitoes for the virus and collect data on dead birds. Mosquitoes transfer West Nile to birds, which can kill them, making bird deaths a reliable indicator of how many mosquitoes are carrying West Nile in a region.

This year, dead birds that tested positive for West Nile have been found in L.A. County as well as Orange, Sacramento, San Diego, Fresno, Merced, Tulare and San Joaquin counties, according to the state’s West Nile website.

A Tustin woman in her 50s was confirmed this week to have been the first human case of West Nile virus in Orange County this year.