ROSEVILLE (CBS13) — Placer County residents are being told to be careful outdoors after test results found an increase in the number of birds and mosquitoes found infected with the West Nile virus.

Disturbing test results show a widening area of Placer County where birds and mosquitoes have been found infected. Officials have announced an elevated risk that has moved into areas never touched before.

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“We’ve actually expanded the area of risk to include most of the northern Roseville area, all the way out in into West Park and a little snippet of Rocklin,” says Ada Barros with Placer County Mosquito & Vector Control District.

It’s not uncommon to find some birds and mosquitoes infected with West Nile this time of year, but officials say this new outbreak is different.

“We’re seeing more activity than we used to in those highly populated areas,” says Joel Buettner, general manager of the district.

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In the district’s lab, scientists are searching for clues to explain the virus. In the meantime, officials say mosquito spraying will likely move into more populated areas and they’re asking for the public’s help identifying areas of standing water or notifying them about any dead birds they can test.

And while they say they don’t want to cause panic, they are emphasizing the possibility more people could contract the West Nile virus from this increase.

According to Barton, “Right now our biggest concern is that there are mosquitoes out there infected with West Nile virus at the same time when people are out there. Out playing golf, going shopping and we’d like them to know there’s a risk there.”

Officials are also urging people to take some basic precautions. Using repellent when outside early in the morning and again around dusk.