Mismatch between Virus Antigens and Antibodies (image) University of Arizona Share Print E-Mail Caption Fatalities by birth year for H5N1 and H7N9: Most patients with birth years prior to 1968 are expected to have been initially exposed, as children, to a group 1 HA. The researchers found that most H5N1 vs. H7N9 mortality in these age groups is caused by the mismatched group 2 H7 HA virus. Conversely, most of those born in 1968 and later were exposed first to a group 2 HA (H3N2, orange shading). The mismatched H5 HA virus causes most mortality in these age groups. Credit Michael Worobey Usage Restrictions This visual may only be used in conjunction with reporting/posting of this news release. Image/video credit must be included exactly as indicated. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.