Global epidemiology of animal influenza infections with explicit virus subtypes until 2016: A spatio-temporal descriptive analysis

Influenza virus, with a global distribution, diverse animal host range and multiple virus subtypes, has caused several pandemics. To better prepare for the emergence of new subtypes and the possible threat of the next pandemic, the global status of animal influenza must be defined and documented. We created a global database of animal influenza events by searching scientific databases and the primary literature on animal influenza-related events up to and including 2016. The temporal, spatial and host distribution of animal influenza and the diversity of influenza subtypes in different regions were analyzed. A total of 70,472 records and 4712 events of animal influenza throughout the world were identified. Events involving subtypes H5N2, H7N7 and H7N9 were relatively constant, with a slow upward trend during the past decade. Asia was the region with the most clusters of events. Poultry was the main host reported in Asia and Africa, and wild birds in Europe and North America. We found that wild birds carried a very rich array of virus subtypes, a warning for the possible generation of reassortment viruses with pandemic potential. Influenza virus subtype diversity - a risk for virus reassortment - was greatest in Asia, North America and Europe. Our database provides a comprehensive overview of the historical and current status of animal influenza events throughout the world. Influenza surveillance needs to be strengthened in some countries and regions to prevent the emergence of new subtypes. Importantly, improvement of the global influenza surveillance system and structures to enable sharing of surveillance data is very much needed to prepare for the next pandemic.