Avian Influenza Viruses
November 26, 2021
The global death toll from COVID-19 reached 5 million on November 1, 2021, but the actual figures are likely much higher (1). In recent history, the 1918 H1N1 flu pandemic caused by an Influenza A (H1N1) virus was the most severe known pandemic, killing more than 50 million people worldwide (2). The sequence analysis of the hemagglutinin (HA) gene suggested that the pandemic virus derived from an avian influenza virus immediately before 1918, possibly through a swine intermediary (3).