The Hippo


May 30, 2020








 E. coli facts

• Pathogenic E. coli is called “Shiga-toxin-producing Escherichia coli,” or STEC.
• 265,000 STEC infections occur each year in the United States
• The most common type is STEC 0157 (36 percent of cases)
• It’s not usually fatal; about 5 to 10 percent of people infected with STEC 0157 develop a life-threatening type of kidney failure. 
• About 30 people die from it every year.
• People at highest risk for severe illness include kids younger than 5, seniors 65 and older and those with weak immune systems.
Source: The Center for Disease Control and Prevention


Bad beef
Anatomy of an E. coli investigation

By Ryan Lessard

 At least 14 people in New Hampshire and neighboring states became violently ill this past summer, with severe stomach cramps, bloody diarrhea and vomiting, all following a meal they ate just a few days before. The cause? E. coli. 

Recent outbreaks
Public health investigators quickly homed in on the source of those E. coli infections, and in July federal food protection officials ultimately recalled more than four tons of beef that had been processed by PT Farm in North Haverhill. 
Since then, a number of other E. coli cases have resulted in recalls — a second, minor recall of lamb products from the same farm in September due to E. coli levels found in the water supply there (nobody got sick) and a multi-state recall in New England where seven people became ill from beef, veal and bison meat produced at Adams Farm Slaughterhouse in Athol, Massachusetts. None of the patients in the Adams Farm case were in New Hampshire, but 10 farms in the state were retailing meat involved in the recall.
“When someone is diagnosed with E. coli … or any other reportable disease, the health care provider or the laboratory is required to report it to us at the health department,” said Beth Daly, the head of the state’s Bureau of Disease Control at the New Hampshire Department of Health and Human Services. She’s also a foodborne disease epidemiologist.
This makes tracking outbreaks easier. Daly said the PT Farm case was relatively straightforward because the first nine case patients were all at the same summer camp. That helped to quickly narrow down what was eaten. And when they narrowed it down to ground beef, they found the beef was purchased directly from the source at the PT Farm retail store.
Then more patients cropped up who had eaten at area restaurants that served beef from the same farm.
From there, Daly said investigators still needed to take steps to confirm what they already knew, but investigations like these are not always so easy.
Scene of the bacterial crime
While some infections can be mild, it’s not often something even the healthiest of patients can handle on their own.
“If you’re sick with it you probably need to be under a doctor’s care,” said Tom Collaro, senior investigator with the USDA’s Food Safety and Inspection Service.
While that may not be fun for the patients, it’s good news for epidemiologists, because the more infected people who see health care providers, the faster investigators can identify outbreaks and track down their sources.
According to the Centers for Disease Control and Prevention, symptoms of an E. coli infection typically appear within one to three days of eating contaminated food. People tend to seek medical help within one to five days of becoming ill, and it takes another one to three days until a stool sample test provides physicians with a diagnosis. Determining it’s part of an outbreak can take two to three weeks from the time a person first gets infected.
Food detectives
E. coli tends to be associated with beef as the bacteria is common in the digestive tracts of most mammals. Contamination can come from its feces, it can be shed in its hide and it can be released if the gut is nicked during the preparation of the carcass. 
Investigators say there are three legs of the stool when it comes to tracking down the source of a foodborne illness like E. coli. The first is epidemiology — the study of the disease’s patterns and causes — the second is laboratory testing and the third is an investigation into the environmental causes. 
The figurative bullet is usually found in a stool sample, and when E. coli is detected, state public health officials are notified and the sample gets sent for further testing. 
Even before that testing is complete, Daly said, the state could already be investigating a possible outbreak. They conduct interviews with the patients based on questionnaires designed to figure out what they ate. The first interview takes about 40 to 45 minutes and goes through about 40 different food items. 
The lab test establishes the strain of E. coli and enters it into a national database run by the CDC called PulseNet. From that, they can see if a cluster of patients has been infected by the same strain. 
Laura Burnworth with the CDC said finding the strain is like finding a fingerprint, but state investigators might already be steps ahead if a big group of patients comes to their attention first. She said that’s what happened in Oregon and Washington when E. coli sickened dozens who had eaten from Chipotle last year. Officials were tracking that outbreak even before they did the fingerprinting. 
Once a cluster is identified, the state embarks on a second round of interviews with the same patients. This is longer than the first one; it takes about an hour and goes through 300 foods.
When they compare their findings, investigators pick out some likely suspects — meals the patients all had in common. But if they all ate the same type of food, the case isn’t closed yet, since certain types of food, like beef, are pretty common in American diets.
“Just because five people in a cluster have eaten ground beef doesn’t mean that’s significant,” Daly said.
This is why epidemiology is crucial to solving these cases. So much time has passed and we remember so little about what we’ve eaten that investigators need to turn to science to narrow down the lineup of suspects. 
That gets harder when patients are spread across state lines. Fingerprinting every E. coli sample and uploading that information to a central database is required for every case because it allows the CDC investigators who review the database daily to find patterns state health officials wouldn’t otherwise notice. 
That’s what happened with the Adams Farm case. Patients appeared in Connecticut, Massachusetts, Pennsylvania and West Virginia. Had it not been for identifying the specific strain of the bacteria, it’s unlikely anybody would have made the the connection. And once that connection is made, they can start the work of tracing the disease back to its source.
Daly said state investigators do two things after they’ve established a few possible food culprits shared by the patients. They pursue their hypotheses by doing a third and final round of interviews with the patients to get at the very specific details of the suspected foods. What variety was it? How was it prepared? Where was it served? Where was it bought? And they survey the patients’ neighbors who aren’t sick so they can use their eating habits as a control group. Once they have a baseline, certain suspects can get pushed into the foreground.
“It implicates a food item statistically,” Daly said. 
But this is not always necessary since, as the PT Farm case demonstrated, a common thread like a summer camp cookout might come up early during the interview process and set investigators on the right track.
“Even, sometimes, a single piece of information that someone will tell us will help to [solve] the whole thing. It will be like a break in the case,” Daly said.
Jennifer Sinatra, an epidemiologist with FSIS, said investigators are sometimes lucky enough to find a smoking gun in the form of leftovers.
“We will try and find out if case patients have leftover product and if they have leftover product that we can test and we find that that product does have the pathogen that has made this person sick, and we can find that it’s the same strain … that’s pretty strong supportive evidence typically to point us in the direction of that product,” Sinatra said.
Short of that, they try to figure out what the common sources were in a cluster of patients with the same infection.
And they have to act quickly, Sinatra said, since they hope to prevent future infections by taking dangerous products off the shelves.
After epidemiologists have done their work to finger a specific food like ground beef, FSIS investigators like Collaro will hit the road.
“Once a product is potentially identified and points of purchases are identified, we’ll go out to each point of purchase to try and trace back that product to a common source,” Collaro said. 
“Through record-keeping, through our observations, through interviews with management and staff, we’ll trace back ground beef through distribution channels all the way to a processing facility or a production facility.” 
Finally, once they find a processing facility that slaughtered the cattle, ground the meat and packaged it for distribution, they can trace it back to a specific slaughter date, as they did in the PT Farm case. 
Based on that information, they can figure out the likely scope and scale of the contamination and issue a recall order accordingly. 
Reached by phone, PT Farm owners declined to be interviewed for this story.   

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