Israel Medical Association Journal

Background: Food-borne pharyngitis outbreaks causing substantial morbidity have been documented.

Objectives: To investigate an outbreak of food-borne Streptococcus beta hemolyticus group A pharyngitis among employees of a high-tech company.

Methods: We received a report on an unusually high rate of morbidity among employees of a company in September 2003. The Tel Aviv District Health Office conducted an epidemiological investigation of the outbreak.

Results: Among the 278 people who attended a company party, 83 people became ill. The overall attack rate was 29.8%. Information was available on 174 of 193 employees and family members who attended the party and worked in the Tel Aviv district. Forty-six of them became ill (attack rate 26.4%). The secondary attack rate was 3.8%. Most cases developed symptoms 24–48 hours following the event. Seven cases had throat cultures positive for Streptococcus beta hemolyticus group A. Three items were significantly associated with becoming sick: spring chicken (odds ratio 2.26, 95% confidence interval 1.11–4.63, P = 0.02), vegetable salad (OR[1] 2.88 95%CI[2] 1.40–5.94, P = 0.003) and corn (OR 7.73, 95%CI 3.18–18.80, P < 0.001). Eating corn remained significantly associated with pharyngitis after controlling for other food items consumed.

Conclusions: We describe the epidemiological investigation of a large food-borne outbreak of Streptococcus beta hemolyticus group A pharyngitis most probably transmitted by corn. No previous publication has implicated corn. Food handlers and the public should be aware that they can transmit diseases to others.. Physicians should be aware that streptococcal pharyngitis could be a food-borne disease and that outbreaks in a non-confined setting may be easily missed.

Contamination of food with streptococci could present with unusual outbreaks that may be difficult to recognize in the early stages. This is demonstrated in a large food-borne outbreak of streptococcal pharyngitis that occurred in 2003 in a factory in Israel. The outbreak was reported to the public health services on July 2 and an epidemiologic investigation was initiated. Cases and controls were interviewed and throat swabs taken. An estimated 212 cases occurred within the first 4 days, the peak occurring on the second day. There was a wave of secondary cases during an additional 11 days. The early signs were of a respiratory illness including sore throat, weakness and fever, with high absenteeism rates suggesting a respiratory illness. As part of a case-control study, cases and controls were interviewed and throat swabs taken. Illness was significantly associated with consumption of egg-mayonnaise salad (odds ratio 4.2, 95% confidence interval 1.4–12.6), suggesting an incubation period of 12–96 hours. The initial respiratory signs of food-borne streptococcal pharyngitis outbreaks could delay the identification of the vehicle of transmission. This could be particularly problematic in the event of deliberate contamination.