In November 2003, a large Hepatitis A outbreak was identified among patrons of a single Pennsylvania restaurant.
Dr Anthony Fiore and colleagues from Atlanta investigated the cause of the outbreak and factors that contributed to its unprecedented size.
Demographic and clinical outcome data were collected from patients with laboratory confirmation of Hepatitis A.
The investigators tested restaurant workers for Hepatitis A.
A case-control study was conducted among patrons who dined at the restaurant in 2003.
|Of 240 patients in the case-control study, 218 had eaten mild salsa
|New England Journal of Medicine|
The investigative team performed sequence analysis on a 315-nucleotide region of viral RNA extracted from serum specimens.
Of 601 patients identified, the team reported that 3 died, and at least 124 were hospitalized.
Of 425 patients who recalled a single dining date at the restaurant, 356 had dined there between October 3 and October 6.
The team noted that among 240 patients in the case-control study, 218 had eaten mild salsa, as compared with 45 of 130 controls, for whom data were available.
A total of 98% of patients and 58% of controls reported having eaten a menu item containing green onions.
The investigators tested all restaurant workers, but none were identified who could have been the source of the outbreak.
The team observed that sequences of Hepatitis A virus from all 170 patients who were tested were identical.
The team noted that Mild salsa, which contained green onions grown in Mexico, was prepared in large batches at the restaurant and provided to all patrons.
Dr Fiore's team commented, “Green onions that were apparently contaminated before arrival at the restaurant caused this unusually large foodborne outbreak of Hepatitis A.”
“The inclusion of contaminated green onions in large batches that were served to all customers contributed to the size of the outbreak.”