Assessing Change in Avian Influenza A

The authors compared epidemiology and virology data from the fourth wave of human cases of avian influenza A H7N9 in China to the preceding waves. The fourth wave had a longer duration, greater geographic spread, a higher proportion of cases in rural areas, and higher percentage patients requiring admission to intensive care. However, the case fatality rate remained at approximately 40% and the authors found no evidence of sustained human to human transmission or increased transmissibility to humans from poultry or environmental exposures.