A study by CDC and China CDC has identified specific risk factors
and exposure risks for human infections with the avian influenza
A (H7N9) virus. Key findings showed that exposure to poultry in
live bird markets was the primary source of H7N9 infections among
people in China. Merely being in a location with poultry was
significantly associated with increased risk of H7N9 infection.
Many cases were only exposed to a market once in the period when
they were likely infected. However, raising poultry at home
and consumption of poultry were not associated with an increased
risk of H7N9 illness. Underlying health conditions that were
significantly associated with H7N9 infections in China included
obesity, chronic obstructive pulmonary disease (COPD), and being
on immunosuppressive medications.
This study was conducted from April to June 2013 in eight Chinese
provinces and used a case-control design. Researchers analyzed
data from 89 patients with laboratory-confirmed H7N9 infection
and 339 controls. Controls were people in China that were matched
to cases by age, sex and neighborhood.