Hundreds of birds across the eastern United States have been dying from a mysterious illness, and wildlife experts aren’t sure what is causing it.

In late May, The Washington Post reported birds in the Washington, D.C., area were starting to die. Since then, six states – Ohio, Kentucky, Indiana, Maryland, Virginia and West Virginia – have reported similar instances.

Laura Kearns, a wildlife biologist with the Ohio Division of Wildlife, spoke with USA TODAY about what symptoms these birds are experiencing, what may be causing this illness and what people could do to help the birds.

“I’ve been in contact with the biologists in Indiana and Kentucky, where this is happening, and they’re reporting similar things,” Kearns said. “There are many different diagnostic labs working on this.”

Birds appear disoriented with bulging eyes

Kearns said not all birds have the same exact symptoms, but one thing is common: physical changes around the eyes.

“Some report crustiness around the eyes, some report like bulging or swollen eyes. And then we’ve also had reports of the eyes being kind of sunken in,” Kearns said.

She added the birds also show neurological symptoms like not being able to keep their heads up or are uncoordinated, saying, “they just kind of seem disoriented.”

What type of birds affected?

The Ohio Division of Wildlife reported blue jays, common grackles, American Robins, European starlings and sparrows have been affected. The Indiana Department of Natural Resources also said Northern cardinals have been affected.

Why is this happening?

The Indiana Department of Natural Resources took samples from the sick birds and they tested negative for the avian flu and the West Nile virus. Samples were then sent to the National Wildlife Health Center. The agency said in early June it was also working alongside the University of Georgia Southeastern Cooperative Wildlife Disease Study and the University of Pennsylvania Wildlife Futures Program.

“We are eagerly awaiting the results from them,” Kearns said.

Could cicadas be a factor?

Brian Evans, an ornithologist with the Smithsonian Migratory Bird Center in Washington, D.C., brought up the idea to the NPR that the illness began to appear around the same time the Brood X cicadas began to emerge. Experts have said eating too many cicadas can hurt a dog’s digestive system because their exoskeletons and shells are hard to digest.

Kearns acknowledged a theory birds may be eating cicadas infected with fungus that rots their bodies as ill birds have been found in areas where there are cicadas present. However, she says sick birds have also been found where there are no cicadas, so it may be something else.

What should people do?

There are multiple things people that have homes birds frequently visit can do to help. Kearns recommends people take down their bird feeders for 7-10 days, or until the mortalities stop occurring.

The Indiana DNR says people should also clean bird feeders and baths with water and 10% bleach solution. People shouldn’t handle birds unless they are wearing disposable gloves and keep pets away from them. If someone encounters a dead bird, they should wear disposable gloves and place birds and gloves in a sealable plastic bag and throw away.