Humans, horses, dogs, whales, seals, birds, cats, ferrets and even raccoons are known to be susceptible to the tiny eight-gene viruses. Researchers in Tennessee have now added giant anteaters to that list.

"Who would have thunk it?" senior author Dr. Melissa Kennedy says with a laugh. "We were pretty amazed."

The February 2007 outbreak, involving 11 adult giant anteaters at Tennessee's Nashville zoo, is reported in an article that will be published in the July issue of the journal Emerging Infectious Diseases. All the anteaters survived the illness.

Beyond the initial "Even anteaters?" reaction, some who study influenza profess to be less taken aback than Kennedy and her co-authors. The virus is so unpredictable, scientists who work in the field expect the unexpected.