On Monday, officials from the US Geological Survey said a ban on bird feeding was precautionary and would avoid the illness spreading further.
The first reports of birds with swollen eyes were in May, with charities calling the blinding illness “terribly scary”. Birds were also seen with an oozing discharge, tremors, or had trouble balancing and walking, officials said. Investigations into the illness are currently ongoing at a handful of laboratories.
"This is significant because it seems to be pretty widespread, and also it's extending for a pretty good period of time,” said Megan Kirchgessner, from Virginia's Department of Wildlife Resources, of the illness “And it's continuing.”
She added that birds would be able to find their own food in warmer months, and by doing so it would avoid the disease spreading at bird feeders put out by the public.
“From a veterinary perspective, especially in the springtime when food is abundant, there's no reason for those feeders to be out,” said Ms Kirchgessner, “And to be perfectly honest, especially in a situation like this, they can do more harm than good.”
There have been at least 325 reports of ill birds, according to officials, with only two species affected, grackles and blue jays.
While there is no evidence that the illness is transmissible to humans or other animals, officials are advising people to take basic precautions with the handling of bird feeders.
“It’s terribly scary. It’s horrifying particularly because we don’t know what this is,” Jim Monsma, the executive director of City Wildlife, an animal charity in Washington DC, said in May. “We don’t know how to treat it. We don’t know how to save these birds.”
Officials said scientists from the USGS National Wildlife Health Center, the University of Georgia's Southeastern Cooperative Wildlife Disease Study and the University of Pennsylvania's Wildlife Futures Program are working to find out more about the illness.
Additional reporting by The Washington Post.
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