The Centers for Disease Control and Prevention should have results later this month that provide more insight into how a Missouri resident, who hadn’t had any contact with infected animals or food, contracted a case of highly pathogenic avian influenza.

A routine flu screening in late summer found the H5N1 virus in a Missouri patient. Unlike the other reported cases of avian flu, this person did not report being in recent contact with animals.

Chances are low that human-to-human spread of bird flu occurred in a group of people who were exposed to a patient infected with the virus in Missouri, US health authorities said.