Forty confirmed cases of E. coli O157:H7 sent 20 people to hospitals in 19 states in an outbreak linked to leafy greens. But the specific type or brand remains unknown and the outbreak is over, reports the federal Centers for Disease Control and Prevention.

An investigation by the CDC and the Food and Drug Administration continues.

Four of the 40 developed hemolytic uremic syndrome (HUS), a type of kidney failure, but no deaths were reported. With its failure to trace the E. coli back to a specific source, CDC says consumers do not need to avoid eating leafy greens in relation to this outbreak.

The FDA completed traceback investigations for several types of leafy greens ill people reported eating. Several farms of interest were identified, but no single ranch was a common source of the leafy greens.

Federal and state investigators conducted site visits on farms of interest and collected environmental samples. FDA is analyzing the samples and continuing their investigations to identify the root cause of this outbreak.

Two other E. coli O157:H7 outbreaks were also declared over on Dec. 18. The first of those involved illnesses that occurred from June 6, 2020, to Oct. 25, 2020. It involved 32 cases in 12 states. Fifteen required hospitalization with one case of the hemolytic uremic syndrome (HUS) and one death. The source of the E. coli contamination hasn’t been determined.

Illnesses for the second outbreak, which was associated with the Nov. 6 recall of romaine lettuce by Tanimura & Antle, occurred between Sept. 2, 2020, and Nov. 6, 2020.  Eighteen confirmed cases in nine states saw six hospitalizations and no deaths.   CDC had not determined if the E. coli infections is what made people sick before the outbreak ended.

“The industry has invested significantly into traceability to facilitate removal of the tainted product from commerce,”The Produce Marketing Association said in a statement issued after both CDC and FDA  declared the leafy greens-related outbreak over. 

“PMA continues to convene experts to identify production practices that have a realistic chance of reducing the risk of contamination and transfer. The risk will never be zero, but we continue to monitor emerging science-based knowledge and support the leafy greens supply chain as they strive to reduce the risk of foodborne illness. If we are to get close to that goal, it will require the sharing of data and a meaningful collaboration of the partners in the industry, academia, and government. It will also require a systems approach and continued investment in food safety research.”

According to the CDC, fresh produce is important for a healthy diet but sometimes becomes contaminated with harmful bacteria or germs. The safest option is to cook produce, or at least wash it.

If you plan to eat your leafy greens raw:

  • Wash your hands for 20 seconds with soap and water before and after preparing leafy greens.
  • Discard outer leaves and any torn or bruised ones.
  • Wash leafy greens even if they are labeled “ready to eat,” “triple-washed,” or “no washing necessary.” Washing removes some germs and dirt, but it does not completely remove all germs.
    • Rinse the leafy greens under running water and use your hands to gently rub the surface of the leaves. If you do not have access to safe tap water, rinse with other drinkable water. such as filtered, bottled, or distilled water.
    • Don’t soak leafy greens in a sink or a bowl filled with water. They can get contaminated with germs in the sink and germs can spread from one leaf to the other leaves.
  • Dry leafy greens with a clean cloth or paper towel.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet is the national sub-typing network of public health and food regulatory agency laboratories coordinated by CDC. 

DNA fingerprinting is performed on E. coli bacteria isolated from ill people by using a standardized laboratory and data analysis method called whole genome sequencing (WGS). CDC PulseNet manages a national database of these sequences that are used to identify possible outbreaks. 

WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people were closely related genetically. This means that people in this outbreak were likely to share a common source of infection.

Illnesses started on dates ranging from Aug. 10, 2020, to Oct. 31, 2020. Ill people ranged in age from 1 to 85 years, with a median age of 33 years, and 60 percent were female. Of 34 ill people with information available, 20 people were hospitalized and four developed hemolytic uremic syndrome (HUS), a type of kidney failure. No deaths were reported. 

WGS analysis was conducted for isolates from 19 ill people; an isolate from 1 ill person was predicted to be resistant to ampicillin and amoxicillin-clavulanic acid, and 18 isolates from ill people were not predicted to be resistant to any antibiotics. Standard antibiotic susceptibility testing by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is currently underway. 

These findings do not affect treatment guidance since antibiotics are not recommended for patients with E. coli O157:H7 infections.

Epidemiologic and traceback evidence showed that leafy greens were the likely source of this outbreak. Investigators were unable to identify a specific type or brand of leafy greens because people in this outbreak reported eating a variety of leafy greens and because different leafy greens are often grown, harvested, and processed together.

State and local public health officials interviewed ill people to determine what they ate and other exposures in the week before they got sick. Of the 23 ill people interviewed, 22 reported eating or maybe eating a variety of leafy greens, including spinach (16) and romaine lettuce (15).

Unless something new pops up,  the year is ending without any active multistate E. coli outbreaks, according to the CDC.

(To sign up for a free subscription to Food Safety News, click here.)