A man with no known contact with a bird flu infected animal nevertheless contracted bird flu. But let’s not panic: “This could still be a one-off case and not the sign of something bigger,” says Scott Hensley, a viral immunologist at Philadelphia’s University of Pennsylvania Perelman School of Medicine.

Since March of this year, the dozen or so cases of humans infected with H5N1 were in people who had contact with infected cows, birds, or other animals. However, in Missouri, a human being was infected even though apparently he had no contact with any animal carriers of the disease. In April, the journal of Nature reported that the bird flu virus “jumped from an infected bird to a cow,” and that cows in six of the United States were infected. Tests of raw milk from those infected cows contained “huge amounts” of the bird flu virus.

The Missouri man had symptoms–nausea, chest pain, diarrhea, vomiting–indicative of H5N1. Yes, he had it, but did not become severely ill and is now fine. Two other people who had contact with the man in the hospital showed signs of illness, but there was nothing conclusive.

Virologist Yoshihiro Kawaoka, University of Wisconsin–Madison, commented that researchers know little about which genetic changes might allow bird flu viruses to better infect humans or to become airborne.

The ultimate question is, can the virus not only infect humans, but be passed to other humans, causing a potentially dangerous outbreak? Researchers are calling for more information about those infected: what they’ve eaten, where they’ve been–perhaps a state fair–and what they’ve been doing, such as cleaning out a bird feeder. They are also awaiting results of antibody testing and looking at genome sequencing from the hospitalized Missouri patient.