Federal health officials announced Thursday that a Missouri resident infected with bird flu did not spread the virus to others, alleviating concerns about potential human-to-human transmission during the current nationwide outbreak affecting poultry and dairy farms.

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,

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.