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- H5N1 is a type of influenza virus that causes a highly infectious, severe respiratory disease in birds called avian influenza (or “bird flu”).
- Human cases of H5N1 avian influenza occur occasionally, but it is difficult to transmit the infection from person to person.
- When people do become infected, the mortality rate is about 60%.
- Almost all cases of H5N1 infection in people have been associated with close contact with infected live or dead birds, or H5N1-contaminated environments.
- The virus does not infect humans easily, and spread from person to person appears to be unusual.