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An outbreak of salmonellosis involving multiple vehicles
Abstract:
A biphasic outbreaks of salmonellosis affected customers and employees of a restaurant in Maine, in October and November, 1979. Salmonella typhimurium was isolated from 27 customers and nine employees. Ten other individuals were ill but did not have specimens taken for culture, and there were four secondary cases including one affecting a laboratory technician. Fourteen individuals (28%) were hospitalized for up to 45 days, and a total of 416 days of work were lost as a result of the outbreak. Two different food items served at the restaurant at separate times were identified as vehicles. In the first part of the outbreak, 37 persons who consumed either egg-based foods (p = 0.003) or salad (p = 0.006) became ill. In the second phase of the outbreak, in late October and November, nine cases were associated with consumption of inadequately refrigerated salad (p = 0.008), but not with egg-based foods. An infected symptomatic food handler prepared the incriminated salad for some members of this latter group. Use of antacids was also associated with illness (p = 0.03). The occurrence of illness over a seven-week period, the implication of several vehicles, and the demonstration of secondary cases suggest that "sporadic" cases of salmonellosis in the community may be linked.
Insights
A restaurant outbreak of Salmonella typhimurium caused illness in customers and employees due to contaminated food. This investigation highlights how multiple food vehicles and secondary cases can link seemingly sporadic salmonellosis infections.
Area of Science:
- Epidemiology
- Foodborne Illness
- Microbiology
Background:
- Biphasic outbreaks of salmonellosis occurred in a Maine restaurant in 1979.
- Salmonella typhimurium was identified as the causative agent, affecting both customers and employees.
Purpose of the Study:
- To investigate the cause and spread of a biphasic salmonellosis outbreak.
- To identify the food vehicles responsible for the outbreak.
- To understand the transmission dynamics, including secondary cases.
Main Methods:
- Case-control study investigating food consumption and illness.
- Microbiological isolation of Salmonella typhimurium from patients.
- Analysis of outbreak timeline and potential transmission routes.
Main Results:
- Two distinct food vehicles (egg-based foods and salad) were implicated in separate outbreak phases.
- Inadequately refrigerated salad was linked to the second phase, with an infected food handler identified.
- Secondary transmission occurred, and antacid use was associated with increased illness risk.
Conclusions:
- The outbreak demonstrated multiple vehicles and secondary transmission, suggesting a link between restaurant-associated outbreaks and community-wide sporadic cases.
- Proper food handling and refrigeration are critical to prevent Salmonella outbreaks.
- Understanding transmission dynamics is key to controlling foodborne illnesses.