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Overview of the Respiratory System

Author(s): Nancy Moreno, PhD, Deanne Erdmann, MS, and Sonia Rahmati Clayton, PhD
Showing Results for: human Return to Presentation

Avian Influenza: H5N1

H5N1 is a variant of influenza A virus that usually does not infect humans. Thus, most humans do not have pre-existing immunity to this strain. Beginning in 1997, more than 100 cases of human infection by bird influenza virus H5N1 have been documented. It is believed that most cases of H5N1 were spread by direct contact with infected poultry, and to date, the virus has not acquired a mechanism for efficient transfer from human to human.

The behavior of the virus may be changing. There is evidence that H5N1 has become more lethal and acquired the ability to replicate in pigs and several other mammalian species. In addition, H5N1 infection resulted in an unusual die-off of 6,000 migratory birds in China in April, 2005.