In 2011, 159 people were infected with the West Nile virus and nine died. Last week alone, 52 new cases were reported to the California Department of Public Health (CDPH) in what the agency said was “the highest level ever detected” in the state.

So far this year, 181 cases and eight deaths in 22 counties have been reported in the state, compared to 101 cases and six deaths at this time last year. Six of the eight deaths were in Northern California and two were in Orange County. Fifteen people died of the virus last year.

This is prime season for the virus, which lasts through September. Humans and animals get West Nile through the bite of an infected mosquito, although it is carried by birds. It is not passed from human to human. Birds with West Nile have been detected in 34 of the state’s 58 counties.

Although most people who are infected do not display serious symptoms, about 1% can develop devastating neurologic illness, like meningitis or encephalitis. Persons over 50 are at higher risk of complications, along with people with diabetes and/or high blood pressure. Less-serious symptoms are flu-like.

Various locales have been spraying pesticides on the ground and from the air since July to control the mosquito population. It is not without controversy. Both the CDPH and the U.S. Environmental Protection Agency (EPA) are OK with spraying the chemicals, which often include pyrethroids and organophosphates.

But others are not. Irva Hertz-Picciotto, environmental epidemiologist with the University of California, Davis, told the Sacramento Bee, “The big concern is the long-term effects that might happen from low level non-acute toxic doses. My concern is for young children and pregnant mothers.” 

Hertz-Picciotto’s concerns arise from a study she conducted of pregnant women living close to agricultural areas where pesticides like organophosphates were applied. She recommends that persons at risk take precautions during spraying by staying indoors.

Stop West Nile Spraying Now, a group in the Davis/Sacramento area, want a permanent cessation in spraying, which it says causes far more harm that the virus. Their website says, “While any death is tragic, and while we strongly support effective preventive measures, comparing the 9 deaths in California in 2011 of people infected with WNv to the 7,000 or more flu and pneumonia-related annual deaths reveals the extent of the official exaggeration. The spraying supposedly justified by an ‘epidemic’ is then a badly out-of-proportion public health response to a relatively small threat.”   

The CDPH does not issue any warnings about the spraying or suggest people take any special precautions. Bruce Hammock, professor in the Entomology & Comprehensive Cancer Center at UC Davis, told the Bee that the greatest danger from spraying was the psychological effect it had on people. “It’s a common societal problem—that we want benefit without risk.”

–Ken Broder

To Learn More:

West Nile Virus at Highest Level Ever in California Mosquitoes (by Susan Abram, Los Angeles Daily News)

West Nile Virus Infections Soar in California (by Victoria Colliver, San Francisco Chronicle)

Dispute Aired over Sacramento County Spraying of West Nile-Targeting Pesticide (by Edward Ortiz, Sacramento Bee)

West Nile Virus at Highest Level Ever in Mosquitoes (California Department of Public Health)

Overkill―Why Pesticide Spraying for West Nile Virus in California May Cause More Harm than Good (by Matt Wilson, Will Sugg and Jasmine Vasavada, Pesticide Watch)