In late October 2022, Chipotle temporarily closed some of its restaurants after customers reported falling ill after eating at locations in Ohio and Michigan. By early November, the fast food chain had closed over 80 stores as it investigated reports of foodborne illness connected to its restaurants. The culprit initially seemed to be romaine lettuce served at the affected Chipotle locations. Romaine lettuce has been linked to past outbreaks of E. coli and salmonella. This article will examine what foodborne pathogen may have contaminated the lettuce served at Chipotle, the symptoms caused by this pathogen, and how lettuce can become contaminated.
What pathogen was detected in the lettuce?
On November 4th, 2022, the Centers for Disease Control and Prevention (CDC) announced that E. coli bacteria was detected in romaine lettuce samples taken from a sick person’s home in Ohio. The particular strain identified was E. coli O157:H7, a Shiga toxin-producing type of E. coli that can cause severe illness.
In total, 37 E. coli cases across 6 states were linked to the outbreak. Of these, 22 people were hospitalized and 8 developed a type of kidney failure called hemolytic uremic syndrome. No deaths were reported. The true number of people infected was likely much higher, as many mild E. coli infections go undiagnosed and unreported.
E. coli O157:H7 produces Shiga toxin, which can damage red blood cells and cause the kidneys to shut down. This strain is commonly spread through contaminated food or water. Previous outbreaks have been linked to lettuce, spinach, and other leafy greens that are eaten raw.
Symptoms of an E. coli O157:H7 infection
People infected with E. coli O157:H7 typically develop symptoms of gastrointestinal illness within 3-4 days after exposure. Symptoms may include:
- Severe stomach cramps
- Diarrhea, often bloody
- Vomiting
- Mild fever
In 5-10% of cases, the infection progresses to the life-threatening hemolytic uremic syndrome (HUS) about a week after the first symptoms appear. HUS results from Shiga toxin damaging red blood cells and platelets. Symptoms of HUS include:
- Decreased urination
- Pale skin
- Fatigue, irritability
- Easy bruising or bleeding
- Swelling of face, hands, feet, or body
HUS can lead to kidney failure, seizures, heart problems, and death. Very young children and the elderly are at highest risk of developing this dangerous complication.
How long do E. coli symptoms last?
For people with mild E. coli infections, symptoms usually resolve within 5-7 days. Recovery may take longer for those who develop HUS. With prompt medical care, most people make a full recovery. However, some may experience lingering effects like high blood pressure or kidney damage after an HUS diagnosis.
How did E. coli contaminate the lettuce?
There are a few ways that fresh produce like lettuce can become contaminated with pathogenic bacteria:
Contaminated irrigation water
E. coli and other pathogens can be present in water sources used to irrigate produce fields. If the water contains animal feces or runoff from nearby cattle farms, for example, it can transfer bacteria onto the lettuce leaves. Proper treatment of irrigation water is needed to prevent this.
Contact with infected animals
Wild animals like deer, boars, and birds may spread E. coli through feces in fields or vegetable processing facilities. Good agricultural practices are needed to limit wild animals getting into produce growing areas and processing plants.
Inadequate cleaning of processing equipment
Lettuce is washed and processed after harvesting. If equipment is not properly cleaned, bacteria can spread between batches of lettuce. Strict sanitation protocols must be followed in produce processing plants to avoid cross-contamination.
Contamination during food prep
Restaurant employees who handle lettuce while ill with something like norovirus can also accidentally contaminate it. Proper hand washing and food safety training in restaurants is key to preventing spread through food prep.
How to prevent E. coli infections from lettuce
Because leafy greens like lettuce are often eaten raw, they can spread pathogens more easily than foods that are cooked at high temperatures. Here are some tips for how consumers can prevent E. coli infections from contaminated lettuce:
- Wash lettuce thoroughly under running water before eating, even pre-washed bagged lettuce.
- Keep uncooked meats separate from produce when grocery shopping, prepping, and storing foods to avoid cross-contamination.
- Cook ground beef thoroughly to an internal temperature of 160°F to kill germs.
- Avoid raw sprouts, which are prone to bacterial contamination.
- People at higher risk for food poisoning (young kids, elderly, pregnant women) should avoid eating salad at restaurants linked to an outbreak.
Conclusion
The multistate E. coli O157:H7 outbreak linked to romaine lettuce served at Chipotle affected dozens of people across 6 states in late 2022. The Shiga toxin-producing bacteria can cause severe gastrointestinal illness and potentially life-threatening complications like hemolytic uremic syndrome. Contaminated irrigation water, animal intrusion, and unclean processing equipment can all lead to lettuce being tainted with pathogens. Consumers should take care to wash lettuce thoroughly, handle it safely in the kitchen, and avoid salad dishes when visiting restaurants implicated in outbreaks to reduce their risk of acquiring an E. coli infection.