A day after the Centers for Disease Control and Prevention said it had yet to identify “a clear source” of infection in a Missouri patient who tested positive for the bird flu virus, the agency quietly disclosed in its weekly influenza report that a close contact was sick around the same time as the Missouri patient but was not tested for influenza.

As bird flu continues to spread through dairy cow herds and poultry flocks, the Missouri case has raised the possibility of human-to-human transmission of bird flu. But officials stressed Thursday there is no evidence of other people being infected and the risk to the general public remains low.

A close contact of a Missouri resident identified as having a human case of the H5N1 avian flu also became sick around the same time, the Centers for Disease Control and Prevention has revealed.