This is indeed a strange disease. The epidemiology suggests it to be of relatively low infectivity, but high severity. This in itself is odd, especially if the causative agent is a virus and the principal mode of spread by coughing/droplet. Also odd is the undoubted existence of “superspreaders”, who can infect very many of their contacts—I can’t think of any parallels to this in respiratory virology.

Perhaps the SARS virus obeys the usual rules of droplet transmitted respiratory infections, and is of high infectivity. However, because of shared antigens, a proportion of the population has an acquired resistance to the new …