West Nile is off to a quick start in California

West Nile virus is off to an early start this year with reports of the disease in 26 California counties, prompting health officials to call on the public to take aggressive preventive measures.

So far, Kern County leads in the number of cases reported of the mosquito-borne disease, with three people who have become ill and 41 dead birds that have tested positive for the virus.

No other county has reported human cases so far this year, but health officials warn that high temperatures that have hit much of the state could prompt a more rapid spread of the disease than last year.

Sixty new cases of dead birds testing positive for the virus were reported last week.

West Nile virus, unheard of in California before 2002, now has its own season: the sizzling summer months.

“The hot spells we are having now are definitely good for the virus,” said Stan Husted, a supervising public health biologist with the California Department of Public Health. “What we want is to have fewer cases than last year, not more.”

State health officials say West Nile is now endemic in California and there is no hope of eradicating it. Although the virus was found in a dead bird in Los Angeles in January this year, it spreads most rapidly in July and August.

The disease is named after the West Nile district of Uganda, where the virus was first isolated; it is commonly found in Africa and Asia.

The first known U.S. case was discovered in New York in 1999. Since then it has spread to 47 other states, Mexico and Canada.

In California, the disease peaked in 2004 when it appeared in all 58 counties, infecting at least 779 people and killing 28. The incidence of the disease has declined each of the last two years, killing seven in 2006.

Health officials say new hot spots for the disease pop up each year in areas where people and animals have not developed immunity to the virus or learned to take preventive measures, including draining standing water and putting screens on windows and doors.

Husted also urged people to prevent mosquito bites by using a repellent containing DEET -- a message he reinforces with the personalized license plate on his car, “UZ DEET.”

In its milder form, West Nile virus causes flu-like symptoms; many people are unknowingly infected without suffering any symptoms. But in its more severe form, it can cause encephalitis, meningitis and death. Older people are more likely to develop severe symptoms than younger people.

Cynthia Jean, coordinator of the state’s West Nile Virus Surveillance Program, said a recent study of California’s 2005 cases found that people with diabetes who contract West Nile virus are four times as likely to contract the severe form of the disease.

As part of the effort to halt the spread of the disease, state and county health workers test dead birds and squirrels to see how many have died from the virus. So far this year, 159 birds have tested positive, compared with 95 last year at this time, Husted said.

In addition, health workers sample mosquitoes in ponds to test for the incidence of the virus. So far, 141 have tested positive, Last year there were 65.

The state also has set up a network of “sentinel chickens” to monitor the spread of the disease. Because chickens develop antibodies when exposed to the virus but do not suffer any symptoms, the state has established 201 flocks of chickens in high-risk zones. So far this year, six chickens have tested positive, compared to seven at this time last year.

In all, the virus has been found in 26 counties this year, compared to 22 at this point last year.

In Los Angeles County, three birds have tested positive. Dr. Laurene Mascola, chief of the acute communicable disease control program at the county Department of Public Health, said the virus can persist year-round because of the region’s warm climate, but it typically peaks in Los Angeles County in late July and August.

Dr. Boyce Dulan, deputy health officer and director of disease control at the Kern County Department of Public Health, said his county has had the highest number of cases for the past three years in part because of the large number of migratory birds that pass through. In addition, he noted, Kern is the state’s third-largest county and has numerous lakes and ponds.

“The early heat this year has provided for an earlier onset of the disease,” he said. “We are trying to get people to realize the risks that are out there and to do something about it.”

A state website, www.westnile.ca.gov, provides more information on West Nile virus.

richard.paddock@latimes.com

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(BEGIN TEXT OF INFOBOX)

Spread of virus

Cases of West Nile virus are up in California compared to this time last year.

Infections year-to-date

*--* 2006 2007* Counties affected 22 26 Human cases 1 3 Horses 0 2 Dead birds 95 159 Mosquito samples 65 141 Sentinel chickens **7 6 Squirrels 0 1

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* As of Friday

** Chickens placed by state health officials in areas where they may become infected and then tested regularly

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For more information: www.westnile.ca.gov

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Source: California Dept. of Public Health

Los Angeles Times