Great piece on H5N1 by Ed Yong, including the following 5 questions (and some answers).
Q1: Why is it so successful"
Q2: Where is it now?
Q3: How does it kill?
Q4: Will it become transmissible in humans?
Q5: What else could cause a pandemic?
Apropos the latter, he says:
"H9N2 may be an equally plausible pandemic candidate.... It generally goes unnoticed, but has hunkered down among Asia's poultry, caused occasional outbreaks in humans and can reassort with seasonal flu. Some strains already have mutations that are associated with greater transmissibility in mammals. H7N7 is similarly widespread and under-reported. In 2003, it flared up in the Netherlands, infecting 89 people and killing a veterinarian. Virologists hope that by understanding the secrets that allow H5N1 to spread and kill, they are in a better position to assess the risk posed by other subtypes."
Via Ed Rybicki