Impact on Humans
- 2009 H1N1 swine flu led to patterns of death and illness not normally seen in influenza infections. Most of the deaths occurred among younger people, including those who were otherwise healthy (11).
- Approximately 90% of estimated hospitalizations and 87% of estimated deaths from April through January 16, 2010 occurred in people younger than 65 years old (1).
- CDC estimates that from April 2009 to January 2010, approximately 57 million cases of 2009 H1N1 occurred in the United States, including 257,000 H1N1-related hospitalizations and about 11,690 deaths (5).
Impact on Other Species
- Influenza A viruses (IAVs) pose a serious threat to public health. and are among the most common causes of human respiratory infections. They have been isolated from many hosts, including human, pigs, horses, dogs, and both wild and domestic birds (9).
- All pandemic influenza viruses, like those of 1918, 1957, 1968, and 2009, ultimately acquired some or all of their gene segments from the avian influenza A gene pool, but the mechanisms by which avian influenza A crosses species barriers, whether causing “dead‐end” infections or onward transmission in the new hosts, are largely unknown (6).
- Pigs have an important role in inter-species transmission of influenza, because they have receptors to both avian and human influenza virus strains (3). They are the intermediate host (“mixing vessel”) for the potentially pandemic-causing generation of influenza A (6).
- Monitoring the global live trade of swine and survey of migratory birds would be beneficial for the prevention and control of IAVs (9).