The outbreak strain of E. coli O157:H7 that has sickened as many as 69 people (46 confirmed, as of June 25th) in 29 states has been circulating in the United States for more than four years, according to CDC records.
Based on the chart displayed in CDC's outbreak investigation report, this strain has been reported in 363 E. coli O157:H7-infected individuals since February 2005. Significant clusters of reported cases occurred in February/March 2005, August 2005 through January 2006, April 2006 through December 2006, and April 2008 through December 2008. The present outbreak may have started as early as March 2009.
Without knowing the genetic fingerprint of the outbreak strain, we can only guess at the precise outbreaks associated with this particular E. coli O157:H7. Here are my best guesses.
- February 2005: Florida farm animal petting zoo outbreak (22 cases in February/March 2005)
- August 2005 - January 2006: Some of these illnesses may be linked to two ground beef recalls initiated in August 2005 and September 2005 by Flanders Provision Co. after CDC linked their meat epidemiologically to E. coli O157:H7 illnesses.
- April 2006 - December 2006: The November/December 2006 outbreak that was traced to contaminated shredded lettuce served at Taco Bell fast food restaurants in the northeast may account for some of these cases.
- April 2008 - December 2008: Iceberg lettuce outbreaks in the United States and Canada (September/October 2008) may have been due to this strain of E. coli O157:H7.
- March 2009 - ?: Nestlé Toll House raw cookie dough.
If my suppositions prove to be correct – and we won't know unless CDC and USDA release the genetic fingerprints for these incidents – this strain of E. coli O157:H7 is now endemic. It has made itself at home right across the United States. As, most likely, one or more other strains of E. coli O157:H7 have done, too.
What does this mean for food safety?
Quite simply, the food industry and its regulators no longer have the luxury of treating E. coli O157:H7 as a niche pathogen – one that is found only in a limited range of food products. This pathogen has kept one step ahead of regulators and the industry for nearly three decades, jumping from dairy cows and petting zoo animals to recreational water, beef, apple cider, salad greens, and sprout seeds. Now it appears to have jumped into raw cookie dough.
E. coli O157:H7 is a hardy microbe – in many ways, hardier than Salmonella. It also is deadlier than Salmonella. Inevitably, E. coli O157:H7 will become as pervasive as Salmonella. Eventually, it might even challenge Salmonella at the top of the list of foodborne pathogens.
This scenario might sound far-fetched, but who would have predicted the contaminated cookie dough outbreak? Certainly not Nestlé's Corporate Quality Assurance group.
It's time to start paying closer attention to E. coli O157:H7 across the entire food spectrum – before this versatile pathogen outflanks us again.