Background

Since 2014, 17 human cases of infection with the newly emerged highly pathogenic avian influenza A(H5N6) virus have been identified in China to date. The epidemiologic characteristics of laboratory-confirmed A(H5N6) cases were compared to A(H5N1) and A(H7N9) cases in mainland China.


Methods

Data on laboratory-confirmed H5N6, H5N1, and H7N9 cases identified in mainland China were analysed to compare epidemiologic characteristics and clinical severity of the cases. Severity of the confirmed H5N6, H5N1 and H7N9 cases was estimated based on the risk of severe outcomes in hospitalized cases.


Results

Reported H5N6 cases were older than H5N1 cases with a higher prevalence of underlying medical conditions but younger than H7N9 cases. Epidemiological time-to-event distributions were similar among cases infected with the three viruses. In comparison to a fatality risk of 70% (30/43) for hospitalized H5N1 cases and 41% (319/782) for hospitalized H7N9 cases, 12 (75%) out of the 16 hospitalized H5N6 cases were fatal, and 15 (94%) required mechanical ventilation.


Conclusions

Similar epidemiologic characteristics and severity were observed in cases of H5N6 and H5N1 virus infection, while severity of H7N9 virus infections appeared lower. Continued surveillance of human infections with avian influenza A viruses remains an essential component of pandemic influenza preparedness.