April 30, 2003

SARS and 6 Degrees

We probably dodged the bullet on this one but it provides a vivid illustration of the level of our interconnection and the vulnerability that might present. The SARS story broke right around the time that the US invaded Iraq and as riveting as the embedded reporting was, I was playing close attention to the scroll at the bottom of the screen and wondering about the priorities of the news media (but that is a different rant).

SARS seems to have had it origin in Guangzhou. It is likely to be a coronavirus and it is possible that close contact between humans and animals in Guangzhou allowed the virus to jump from animals to humans.

What is fascinating and scary about SARS is how fast and widely it spread. The speed of spreading is due to the biology of humans and the virus. The virus could survive for fairly long periods outside of the human body and is spread in droplets related to the coughing and other symptoms of the disease. In addition it seems that some people are extremely efficient at spreading the disease.

The geography of the spreading is primarily related to the extent that humans move around the globe. It has been observed many times that replacing sea voyages with air travel allows people to get from point A to point B much more rapidly than the incubation period of the disease. This allows the pathogen to mix well around the globe.

The reason I am writing about this today is an article in the New York Times. It seems that a case of SARS has been identified in the very exclusive enclave that houses the senior leadership of the Communist party in China. To me this highlights the interconnection elements of the epidemic.

Think of SARS as a tracer. There is a path from any new case to an old case. Thus there is a path from the elite of Zhongnanhai to the outlaws of Guangzhou. More impressive is that there are fairly short paths from China to all of the developed economies in the northern hemisphere and many of the better developed economies in the southern hemisphere. All of this illustrates the importance of the ideas around 6 degrees of separation.

It is especially sobering to imagine the what it would like if instead of about 6% mortality, SARS had 25% mortality and rather than superspreaders being rare, they were the norm. If this were the case we would probably recognize the problem faster than we did this time round, but given our experience in Toronto, it is not hard to imagine falling behind the curve and not being able to recover.