Blood tests of several people who were in contact with a patient in Missouri who caught H5N1 bird flu without any known exposure to infected animals reveal at least one of them — a person who lived in the same house and had symptoms at the same time — also had the virus,

The bird flu virus hasn't yet spread from person to person, the CDC said Thursday, releasing findings from a monthslong probe into a hospitalized Missouri patient.

New test results suggest Missouri did not see a cluster of bird flu cases, a possibility that some experts had feared.

FILE - This 2005 electron microscope image shows an avian influenza A H5N1 virion. NEW YORK (AP) — Health officials said Thursday that there's no evidence bird flu is spreading between people after investigating a mysterious infection in Missouri.

The case concerned health officials and experts because human-to-human transmission of the H5N1 strain of avian influenza could mark the start of a new pandemic.

Two people sharing a home caught the virus without known exposure to animals. More than 30 human cases have been reported in the United States.

Centers for Disease Control and Prevention officials told reporters Thursday that there is no evidence that there has been any case of human-to-human spread of H5N1 bird flu in the mysterious situation reported last month in which several people in Missouri suffered illnesses unrelated to known animal contact.

As H5N1 bird flu continues to spread wildly among California dairy herds and farmworkers, federal health officials on Thursday offered some relatively good news about Missouri: The wily avian influenza virus does not appear to have spread from the state's sole human case, which otherwise remains a mystery.

The Centers for Disease Control and Prevention (CDC) announced Thursday that there is no evidence of human-to-human transmission of the H5N1 bird flu virus in a recent Missouri case, despite a rise in infections among farmworkers.