Human influenza is a viral respiratory disease that often results in a high mor- bidity and considerable mortality rate in both humans and domestic animals1,2. Influenza epidemics vary in severity from year to year. This disease can also wreak economic havoc on a community because of the number of workdays lost to ill- ness and the resulting impact on business2,3. Therefore, studying the influenza virus is of considerable importance, both for the discovery of practical treatments for the disease and for the development of vaccines to prevent it4.