Avian influenza without the avian

Southeast Asia, including China, is where most cases of human avian influenza occur. Nearly all the cases involve human contact with poultry. Evidently, higher body temperatures, are required for the virus to successfully replicate to the point where viruses populate the respiratory system. Birds have a slightly higher (~42 C) body temperature than humans (37 C). Gary Ritchison has a fantastic web page explaining avian body temperatures and metabolism.

Recently, a case report described a young adult that traveled from Canada to Beijing for vacation and there the person contracted A H5N1 influenza and died. The individual started feeling sick on December 27 and died January 2, 2014. The kicker is that this person did not have contact with live poultry. How this person came in contact with the virus is currently a mystery. 

A of A H5N1 refers to the serotype and A and B are typical. A is more common in birds and B is more typical of the seasonal influenza that circulate in humans. C also occurs in humans but is not associated with pandemics.  H refers to the hemagglutinin receptor on the virus surface and there are 17 subtypes. N refers to the neuraminidase receptor and there are 10 subtypes. Hemagglutinin determines host range - how many different animals the virus can infect. Neuramindase affects pathogenicity - how sick you get. Avian or human or porcine (pig) refers to the origin of the virus. One interesting property of these viruses is that they can switch hosts and also recombine in a host such that a bird infected with H5N9 and N1H1 can create N5H1.       
Many serotypes of avian influenza circulate around the globe. Within the US, a few serotypes circulate that impacts the poultry industry but not humans directly (yet). Although most cases of influenza occur in se Asia, cases have been reported across Asia and a fewer number in Europe and Africa. There is some worry that H5N1 could reach the US through migratory birds. A few birds, mostly waterfowl and cranes, breed in the far northeast corner of Asia but split their migration between Asia and North America. One example is the Sandhill Crane, some of which breed in Asia, migrate through Alaska and Canada, and winter in Texas. The concern is that these birds will mix with infected birds and pass H5N1 to North American cranes. The good news: H5N1 is also deadly to birds so this decreases the probability that infected birds will make the trip. The bad news: stopover habitat for cranes is decreases and concentrating them at higher densities. 

References:

• CDC: Types of Influenza Viruses
• Clark, L. and J. Hall (2006). "Avian influenza in wild birds: status as reservoirs, and risks to humans and agriculture." Ornithological Monographs 60: 3-29.
• Fraser, C., et al. (2009). "Pandemic Potential of a Strain of Influenza A (H1N1): Early Findings." Science 324(5934): 1557-1561.
• Normile, D. (2006). "AVIAN INFLUENZA: Evidence Points to Migratory Birds in H5N1 Spread." Science 311(5765): 1225-.