This is where we are with bird flu at the moment: the awkward space between watchful waiting and all-out panic mode. The risks may still be minimal, but the stakes are very high—and each new piece of information seems to make the situation only a bit less stable than it was before.

Just how deadly is the H5N1 avian flu? The virus, which is currently sweeping through U.S. dairy herds, rarely jumps to human beings, at least for now. But when it does, the consequences can be grave: The World Health Organization reports that 52 percent of people known to be infected with H5N1 have died from the disease.

A new human bird flu case in Missouri suggests the virus could pose a more significant threat. Why experts are concerned.

Last Friday, the Missouri health department announced a recent human case of bird flu. What’s unsettling about the case is that the patient — hospitalized on August 22 and later released — is the first among 15 people infected in the US who didn’t report having contact with animals.