An unusual Hollywood look at molecular biology

October 24, 2012

Posted on April 28, 2012

Hollywood offerings that take on epidemics invariably play fast and loose with the facts, so it’s refreshing to see one that adheres to rigorous scientific accuracy. Contagion (Warner; directed by Steven Soderbergh), which made the rounds last year, was produced in cooperation with the CDC. From viewing this film, their enthusiastic participation is hardly surprising. This production is well-crafted and suspenseful, concerning a catastrophic pandemic, caused by a meningoencephalitis virus. As the virus moves from host to host it recombines and picks up genome parts from various mammals that come in contact with one another in the course of food processing in China. By the time it enters the human population, it has acquired superbug status.

In this film there are no people turned into zombies, no pod people, no recombined critters bursting out of the lab, no doomsday machine that destroys the human race and no scientists or pharma executives plotting evil schemes to take over the world. The film plays by the book and the conclusion is exactly what epidemiologists predict would happen if a virus were to morph into a highly lethal, easily transmissible agent.

However, I think the most interesting question raised by the film is not whether it is scientifically accurate in the way it depicts the unfolding of a modern plague, but what is the actual probability of such an event occurring. We really don’t know the answer, but we can make a guess, based on Baysian probability and the historical record. Assuming that conditions favoring epidemics haven’t changed that much in the past sixty years, the probability of a world wide epidemic caused by a newly-evolving pathogen, spreading like lightening through the naïve population is less than 1 in 60 per year, plus/minus the statistical error associated with this estimate. This clearly doesn’t include HIV/AIDS, which is not respiratory and is spread only through sexual contact.

This may not strike you as a very satisfactory answer, but unless such a cataclysm arrives on our doorstep, it will be the best that we can come up with.

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