Apr 25, 2018 - Health

Where the romaine lettuce E. coli outbreak hit hardest

The Centers for Disease Control and Prevention says it's using whole genome testing and on-the-ground investigation to try to determine why the current E. coli outbreak from romaine lettuce is more virulent than normal — about half of all people affected have been hospitalized .

Data: Centers for Disease Control; Cartogram: Lazaro Gamio/Axios
Data: Centers for Disease Control; Cartogram: Lazaro Gamio/Axios

What's new: The E. coli outbreak stemming from romaine lettuce grown in Yuma, Ariz., has spread to 19 states and infected at least 84 people, of whom 42 have been hospitalized with 9 suffering from the dangerous hemolytic uremic syndrome, according to a CDC update today.

Threat level: Matthew Wise, deputy branch chief of CDC's Outbreak Response, tells Axios the CDC has confirmed the pathogen is E. coli 157:H7, which is part of the Shiga toxin-producing strain, but they don't know why so many patients need to be hospitalized.

"157:H7 can be a very severe illness, but [50%] is a much higher hospitalization [rate] than we expect," Wise says. "We're doing whole genome sequencing to see if there's anything unique or unusual in this particular strain."

Benjamin Chapman, food safety specialist and associate professor of North Carolina State University, tells Axios that normally the 157:H7 has about a 25%–30% hospitalization rate. He says the higher rate now could be because the strain "picked up genes from other bacteria which cause toxins [in] us," during its normal evolutionary process.

The big question: This episode of E. coli 157:H7 is one of 7 main multistate foodborne outbreaks of E. coli and salmonella that CDC has investigated in 2018. While this appears high compared with 2017 (which had a total of 8 including listeria and cyclospora), it's too early to tell if this is a new trend for the year, Wise and Chapman both say.

  • Chapman says one reason it appears higher is that "we are getting better at connecting the dots, nationally." He says with new safety standards and systems to identify outbreaks, "food is probably safer now than it was for the last 50 years."

Looking ahead: Wise says the CDC is focused on improving via 2 programs:

  1. An increase of funds to the state health departments so they can better track, report and halt outbreaks.
  2. A transition to whole genome sequencing during outbreaks, which should enable officials to see which illness is spreading where. They've completed a similar program for listeria, and the program for salmonella and E. coli should be finished by late 2018–early 2019.

Some challenges facing the CDC:

  • New lack of cultures: Chapman says the state public health system encourages new testing called culture independent diagnostic tests (CIDTs), which can quickly identify pathogen DNA shards but uses up the stool sample that the federal investigators need to be cultured. "It's a challenge," Wise says, because clinicians want the faster CIDT results but "the whole system relies upon the health care facilities to culture the bacteria."
  • IG report: While not directly part of the CDC, the Food and Drug Administration was checked out by the Inspector General's office and its food recall program was found inefficient and ineffective.
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