<qa>  What is the current threat of a future pandemic?Although avian influenza does not usually affect humans, increasing numbers of cases of human infection from avian influenza virus H5N1 have been reported in the last several years. Because all influenza viruses have the ability to modify, there is concern that this trend of increasing cases may pose a threat of a future pandemic with a new H5N1 virus that could spread easily from person to person. 