Remember that question on the last pset that asked what determined what viral syndromes a virus will produce? Well, tissue tropism definitely affects the syndromes produced by H5N1 and Human Influenza A, a study from the Netherlands reports. They tested which cells these viruses targeted in their hosts. For Human Influenza, they found it binds strongly to tracheal and bronchial cells, and less so in the bronchioles or alveoli. H5N1, however, attached strongly to the bronchioloes and alveoli- thereby explaining why it causes severe alveolitis (pneumonia) whereas human influenza causes tracheobronchitis. Additionally, the tested which animal models are most effective and found that ferrets, pigs, and cats resemble how viruses like H5N1 attach in humans.
A good summary: http://www.sciencedaily.com/releases/2007/10/071009132014.htm
The actual article from American Journal of Pathology: