Why This E. Coli Outbreak Has Me Scared

The E. coli outbreak that started in Germany is getting bigger and a lot scarier. Ten countries have reported a total of 1,614 severe cases to the European branch of the World Health Organization as of early June 2. Thousands more have no doubt fallen ill with less severe symptoms. On June 1, the U.S. Centers for Disease Control reported two cases (both travelers) in the U.S. of infection with the strain, called EHEC 0104:H4, and is asking state health departments to be on the lookout for more.*

It is still the early days in the outbreak but as a science journalist, I have three main questions for which I would really like to find a few answers.

1. Where did this rare EHEC 0104:H4 strain come from? I'm not talking about which country it came from but rather how did it develop? Given how quickly and how widespread the outbreak started, I'm particularly interested to learn if any particular industrial agriculture techniques—like liquid manure spreaders—were involved?**

2. Why are adults (and particularly women) being more severely affected than children or the elderly? Perhaps this is just a fluke—for instance, women probably eat more greens than men. Or is there some underlying biological reason—such as an overly robust inflammatory response to the infection called a cytokine storm, as has happened in other toxic E. coli outbreaks?

3. What is the likelihood that this new EHEC 0104:H4 might pick up even more genes that confer resistance to antibiotics? Part of the reason this strain is deadly is because it has picked up the genes to make two different deadly toxins (one that causes bloody diarrhea and the other that attacks the kidneys). And the Robert Koch Institute in Germany has determined that EHEC 00104:H4 strain is also resistant to 14 different antibiotics. Fortunately, it is still susceptible to two of the carbapenem antibiotics (imipenem and meropenem).

I shudder to think what would happen if EHEC 0104:H4 picked up the genes that confer resistance to carbapenems, which are drugs of last resort for gram-negative bacteria such as E. coli. As Maryn McKenna reported in "The Enemy Within" (preview) back in April, carbapenem resistance genes are now proliferating around the world and have already spread to a few strains of E. coli. Given how frequently severe E. coli outbreaks have occurred in recent years, it seems like only a matter of time before we have an E. coli outbreak that is both extremely deadly and completely immune to antibiotics.

Image: Courtesy of Agriculture and Agri-Food Canada

*Correction (6/2/11): The name of the current strain was corrected throughout the post.

**Clarification (6/2/11): A sentence was deleted after publication because it attributed the origin of a 2006 E. coli outbreak in California to chicken manure. According to the FDA, however, that outbreak's origin remains inconclusive.