Living in South China I have become rather obsessed with the situation surrounding Severe Acute Respiratory Syndrome (SARS). With all the thought I have put towards it, one thing that doesn't quite make sense is virulent nature related to this strain of human Coronavirus, as compared to the relatively low number of infections. At current, there are just under 2000 -known- infections. In a region with about 100M packed population that does not even register. At the same time, case studies have documented the very high virulence -or infectiousness- associated with this virus.

Thus, I have two thoughts:

1) The virus sheds but only a very short time
or,
2) Could some (a lot, I guess) individuals have immunity.

Any qualified response would be much appreciated.

Thanks,
Jon

I've just heard the rumor of "more than reported" cases in Vietnam. To the tune of over 10,000 ppl ! They fear it is a chemical attack. The person who visited the region was told he should leave asap, and that there are far more cases that are not reported. Scary.
Canada is now affected, thats tooooo close to home.

I think that what you are asking relates directly to individual susceptibility.

Basically, it does not matter how virulent something is, if a person is not susceptible to it at a particular time, then no matter how virulent, they will not beceome infected. The same principle works with flu to a stomach virus. You could hang around friends who have got the flu or a stomach virus and you might be fine, showing that you are not susceptible. However, another friend could hang around and become ill with either the flu or stomach virus and this would mean that they had some susceptibility that enabled them to get it.

If you immune system is strong, then you will not be as susceptible.