Washington ? Loudoun County, Va., officials have notified the parents of nearly 1,000 girls in the Washington region that the youngsters may have been exposed to the deadly rabies virus at a local Girl Scout camp and should consider getting a month-long series of protective vaccinations – the largest proactive rabies outreach effort ever conducted in the United States, according to federal authorities.

The chance that any of the girls have been infected with rabies – from bats that were found sharing the girls’ sleeping shelters at Camp Potomac Woods near Leesburg, Va. – is small, officials said. All five bats tested so far were negative for the disease.

But because about 1 percent of bats do carry rabies and can bite children in their sleep without waking them – and because the disease, once symptoms appear, is incurable – authorities are urging parents to question their children closely about whether the shelters they slept in were among those inhabited by the bats, and what kind of contact they may have had.

At least 14 girls have begun the series of shots, local officials said, including all of the children so far notified who were deemed most likely to have had contact with a bat. But the parents of about 400 children, including a handful of girls that officials believe slept in shelters with bats, are slated for aggressive telephone queries this week.

“We think the risk is extremely small, but we can’t say there is no risk,” said Loudoun County Health Department Director David Goodfriend.