Zimmer on E. coli and bioterror

2 minute read

I very much liked Carl Zimmer's Slate piece about foodborne pathogens and their lessons for defending against bioterrorism. Zimmer has a book about E. coli coming out later this spring, and he visits the topic of the 2006 outbreaks of an especially virulent strain.

This worrisome trend led a team of scientists based at Michigan State University to take a look at the DNA of the bacteria. The researchers compared bacteria from recent outbreaks with hundreds of others samples and published the results last Monday. The scientists drew an evolutionary tree based on the differences in the bacteria's genes. One branch of the tree -- the one that caused the spinach and lettuce outbreaks in 2006 -- is significantly more likely to make people sick than the others. And they found that this lineage has been exploding in recent years. In 2002, it accounted for 10 percent of the E. coli cases recorded in Michigan. In 2006, it accounted for 46 percent.

Whole-genome sequencing found large deletions and insertions of hundreds of genes in the newer virulent clade. Zimmer brings our attention to the complexity of the mechanisms that determine virulence. At present, science still can't predict how these genes will affect the pathogens. On this grounds, one may argue that the prospects are low that an enemy state or mad scientist will soon be able to create such a dangerous strain deliberately.

But this is not grounds to celebrate, since nature is busily creating dangerous strains for us. Natural selection does not design its products in a single leap of invention, but it sifts many millions of variants much more efficiently than any human laboratory.

I think that the last paragraph contains the essential lesson.

But this ignorance [of which genes must be altered to make a killer pathogen] is not cause for much comfort. Even if we don't need to worry about synthetic bacteria just yet, we do need to worry about new pathogens evolving right in our own backyard (or, rather, our own feedlots and factory farms). As things stand, we become vaguely aware of these bacteria only once they've been sickening and killing for years.

Sure, it may be difficult to engineer a more virulent pathogen for bioterror. But it is pretty easy to use the ones we already have. The evil genius is much less a threat than nature. And a saboteur looking to replicate small-scale terror on the order of the D. C. sniper may find hundreds of victims by contaminating one line of the vast American food web.

Defending against this kind of terror is the same task as defending against nature.