Hundreds of people may have been exposed to rabies after staying in cabins infested with bats at Wyoming’s Grand Teton National Park.

As many as 500 visitors who stayed in eight cabins at Jackson Lake Lodge between May and late July may be at risk, state health officials said. The cabins have been closed since July 27, when the infestation was first discovered.

So far, none of the bats collected from the cabins have tested positive for rabies. Three or four tested negative, and one could not be tested because of damaged tissue, state veterinarian Dr. Emily Curren told CNN.

But experts suspect dozens more bats lived in the attics above the cabins.

“There’s no way for us to know for certain about every single bat that got into these rooms,” Curren said.

Rabies is almost always deadly once symptoms — such as fever, muscle aches, vomiting, or itching — appear. 

The good news is that early treatment with a series of five shots over two weeks is highly effective at preventing illness, Dr. Alexia Harrist, Wyoming’s state health officer, said in a report from CNN. The shots are usually given in the upper arm or thigh.

“What we’re really concerned about is people who saw bats in their rooms and people who might have had direct contact with a bat,” Harrist explained.

Officials are trying to reach people in 38 states and seven countries who stayed in cabins 516, 518, 520, 522, 524, 526, 528 and 530 this year. Anyone who hasn’t been contacted but stayed in one of these cabins should speak to a doctor immediately, Harrist said.

Children and deep sleepers may be at higher risk if a bat was present in their room, since they may not realize they were bitten.

The Grand Teton Lodge Company has kept the cabins closed and installed devices to keep bats from re-entering the buildings. 

Park officials said there are no plans to kill the bats, which typically live in colonies of 30 to 100, Curren explained.

Unless they stayed at the lodge, health officials emphasized that visitors to the Jackson Lake Lodge area — including those attending the annual Federal Reserve economic symposium in August — do not face any risk.

“The lodge company has done a fantastic job of doing their due diligence of making sure everyone that is coming in for that, and for all other visits this year, are going to be as safe as possible,” Curren stated.