June 2020, Red Seaweed Outbreak


In 2020, red seaweed was associated with an outbreak of E. coli O7:H4 in Japan. Imported in 2017, the red seaweed was contaminated with a strain of E. coli that carries the astAgene for enteroaggregative E. coli heat-stable enterotoxin 1 (EAST 1). The gene was detected in fecal specimens of patients and usually causes relatively mild symptoms.  

According to the Center for Disease Control (CDC), symptoms of E. coli food poisoning include stomach cramps, diarrhea (often bloody), vomiting, and sometimes a fever. People start developing symptoms anywhere from 1 to 10 days after exposure and usually recover within 5 to 7 days. Some infections are mild, while others can be severe or life threatening. A health provider should be contacted if diarrhea lasts more than 3 days or a fever is higher than 102 F.  

By June 2020, elementary and junior high school students in Yashio, Saitama, began displaying gastroenteritis symptoms such as diarrhea and abdominal pain. An estimate of 2,958 students from 15 public schools in Yashio became ill. The common denominator was a school lunch provided by a private meal supplier and consumed by all patients. The patients experienced diarrhea, abdominal pain, and fever.  

The investigation involved a collection of fecal specimens from patients not receiving antibiotics, food sample from the lunch, and swabs of kitchen facilities. The samples were grown on culture plates to confirm the presence of astAgene. 14 patients’ samples and 2 seaweed salad samples were positive for E. coli O7:H4. Coliforms were found in the red seaweed by the manufacturer during self-inspection but were not detected during the import inspection or when it was sold to the manufacturer.   

No other outbreaks have been reported from the same lot number, so the source of the contamination is unknown.  

For more information visit the Food Safety News website at: https://www.foodsafetynews.com/2021/12/e-coli-outbreak-involving-thousands-in-japan-traced-to-red-seaweed/?utm_source=Food+Safety+News&utm_campaign=6f5f6f7495-RSS_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_f46cc10150-6f5f6f7495-40040643.  

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