Between 31 March and 21 April 2013, 102 laboratory-confirmed influenza A(H7N9) infections have been reported in six provinces of China. Using survey data on age-specific rates of exposure to live poultry in China, we estimated that risk of serious illness after infection is 5.1 times higher in persons 65 years and older versus younger ages. Our results suggest that many unidentified mild influenza A(H7N9) infections may have occurred, with a lower bound of 210–550 infections to date.
Cowling BJ, Freeman G, Wong JY, Wu P, Liao Q, Lau EH, Wu JT, Fielding R, Leung GM. (2013). Preliminary inferences on the age-specific seriousness of human disease caused by avian influenza A(H7N9) infections in China, March to April 2013. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin, 18(19)