You'll catch your death of cold - a speculation about the SARS outbreaks -
We have all kind of folk injunctions about the danger of getting a cold - like don't go outside with wet hair. That makes sense when you consider that most homes were poorly heated in the days before central heating. It was very easy to develop hypothermia. Toss in poor nutrition and a cold could be a serious business.
Here's where the speculation comes in -
1. The natural history of most diseases is that the organism starts out by killing all the hosts. The organisms that survive to spread their genes are the ones who make the host sick enough to spread the organism (cough, cough) but not too sick to be among a lot of people. Thus, most illnesses move to becoming less lethal.( at least not immediately). For example - when Syphilis first hit Europe, it was a devastating disease that killed in days and rotted peoples' faces. The spirochete that survived was one that stayed hidden long enough for the victim to spread it to sexual partners.
2. SARS is caused by a coronavirus, as is the common cold.
3. So, maybe this isn't the first time a SARS like illness has emerged. Maybe there have been waves of this illness as different coronaviruses encountered humans and evolved to a detente.