Conditions Could Boost Risk of West Nile

Heavy rains and warm weather in recent months could boost the mosquito population, possibly increasing the risk of exposure to the West Nile virus this summer, state health officials said last week.

It is difficult to forecast the West Nile season, which lasts from June through October, because so many factors are involved, the officials said.

But recent climactic conditions suggest that people would do well to repair screen doors and take other preventive measures in coming weeks, said Vicki Kramer, chief of the vector-borne disease section at the state Department of Health Services.

“We certainly have a lot of standing water,” Kramer said, “and the more standing water you have, typically, the more opportunities you have for mosquito breeding.”

West Nile is frequently passed to humans through mosquitoes that have fed on infected birds.

About 80% of humans infected with the virus don’t realize it. Nearly 20% experience mild to moderate flu-like symptoms. In fewer than 1% of cases, a potentially fatal complication, such as encephalitis or meningitis, can develop.

West Nile was first diagnosed in California in 2002, according to the state health department. The state logged 935 cases last year, including, 47 in Los Angeles County, 17 in Orange County, 104 in Riverside County, 35 in San Bernardino County and one in Ventura County.

There were 19 fatalities statewide last year, with no deaths in Los Angeles, Orange and Ventura counties. Five deaths were reported in Riverside County and one in San Bernardino County.

Nationally, the number of West Nile cases has fallen dramatically from the peak of 9,862 in 2003, according to the U.S. Centers for Disease Control and Prevention. In 2004, 2,539 cases were reported and last year, 2,949 cases.

Robert Saviskas, the executive director for vector-borne disease control in west Los Angeles County, said simple steps could reduce the chance of exposure to the virus.

Most important, Saviskas said, is getting rid of standing water near homes. Clear out clogged rain gutters, fix leaky sprinklers and dump out the water under planters, he said.

He also suggested wearing long pants and long-sleeved shirts when outside around dawn and dusk -- the periods mosquitoes in Southern California are most active -- and spraying exposed skin with insect repellent containing DEET or picaridin.

“It’s things that we don’t often think about,” he said, noting that mosquitoes rarely travel more than one or two blocks to feed. The fewer mosquitoes there are, “the less likelihood there is for the disease to be transmitted,” Saviskas said.