West Nile spraying in Santa Ana halted; cases continue to climb

Health officials have halted plans to spray neighborhoods in Santa Ana as part of an effort to combat what’s become the worst outbreak of West Nile virus ever recorded in Orange County.

The number of people infected with the virus has increased across the state, but Orange County has been particularly hard hit. There have been three deaths and 94 reported infections attributed to the virus, far surpassing the 13 cases recorded last year.

The plan to spray the densely-packed Santa Ana neighborhoods was postponed indefinitely because of weather, the Orange County Vector Control District said in a statement.

For the spraying to be effective, county officials said they need cool evening temperatures and a slight breeze – neither condition is in the forecast for the next 10 days.

The virus is usually transmitted to humans from a bite by an infected mosquito and can cause flu-like symptoms and, in rare instances, death. For most people, the risk of serious illness is low. People 50 or older have the greatest risk of developing serious complications.

Santa Ana had been selected as the first Orange County city to spray because it has “tested consistently positive for the virus over and over again,” said Jared Dever, spokesman for the county’s vector control.

Officials had been waiting to see how effective the spraying would be in Santa Ana before trying it in other hard-hit areas such as Anaheim, Fullerton and Orange.

Spraying, or fogging, is the only known way to control the population of adult mosquitoes, Dever said. It would have marked the first year county officials had taken such an extreme measure in a dense, urban population, he said.

The active ingredient in the pesticide, AquaAnvil, poses a minimal risk to human health and the environment, according to the California Environmental Protection Agency. It will not stain stucco or damage cars or house paint, Dever said. The county has used the fogging trucks routinely on wetlands and other open spaces in the past.

Officials this summer have tried other ways to break the cycles of virus transmission, but “it hasn’t helped to the point that we wish it would,” Dever said.

West Nile reports are up across the state. Ron Chapman, director of the California Department of Public Health, said this week that the proportion of mosquitoes infected with West Nile is at the highest level ever detected in the state.

So far this year, 37 California counties have detected the virus. At least 181 cases have been reported to the agency — a significant increase compared with the 101 cases reported by this time last year. The five-year average at this time of year is 56 reported cases. There have been nine West Nile-related death so far.

“We expect to see more people become infected as this is the time of year when the risk of infection is the highest,” Chapman said in a statement.

Los Angeles County this year has reported 25 cases, including one death, with the largest numbers in the San Fernando Valley and the South Bay, according to the Los Angeles County Department of Public Health.

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Steve Marble contributed to this report.