Finding infected mosquitoes nearby reinforces the importance of draining standing water and wearing protective clothing or mosquito repellent when outdoors. 'Now that the virus is here, people need more than ever to protect themselves.'

For two years, health officials have watched and reported dead birds with the virus as part of an early warning system.

On Monday, the stakes rose. Officials reported the first documented case in the region of infection in the insects that spread the virus to people.

"This means the virus is near. A bird with it could have flown in from somewhere else," said Deborah Bass, a spokeswoman for the Contra Costa Mosquito and Vector Control District. "Mosquitoes travel less than two miles."

Young, Elderly Most Vulnerable

Most people with West Nile virus show no symptoms, but some people, especially the young and elderly, can die.

Crews scooped up the infected mosquitoes south of Brentwood near the junction of Marsh Creek Road and Walnut Boulevard. The work was part of the district's routine surveillance that has tested 97 samples of mosquitoes this year.

Until this batch, Contra Costa had not documented infected mosquitoes. Neither had other Bay Area counties, although Sacramento and San Joaquin counties have, according to the state's official West Nile virus Web site.

Bass said the new finding reinforces the importance that people drain standing water and wear protective clothing or mosquito repellent when outdoors.

"Now that the virus is here," Bass said, "people need more than ever to protect themselves."

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