Pattern Analysis of Pandemic/Epidemic/Reassortment of Influenza Virus

Influenza viruses, which are responsible for annual outbreaks, can exist in any of 198 possible influenza subtypes resulting from the combinations of 18 hemagglutinin and 11 neuraminidase types. However, the number of sub- types capable of infecting humans has never been predicted or investigated. In- fluenza virus outbreaks that occur every year can be categorized as follows: a pandemic with high infectivity and mortality, a regional epidemic, or a recom- bination event leading to reassortment. Investigating changes in influenza vi- ruses through pattern analysis of viruses responsible for each outbreak is an im- portant research tool that can help to predict the zoonotic characteristics of in- fluenza viruses.