The avian flu virus H5N1 is considered a greater long-term threat than the swine flu virus H1N1 because __________.

• A. it is more readily transmitted between human hosts
• B. more people eat chicken meat than pork
• C. H5N1 is a DNA virus and the similarity of genome chemistry can promote greater virulence and therefore the likelihood of death in humans
• D. H5N1 has a greater tendency to become a prophage
• E. it has a significantly higher mortality rate