What is the next step in managing an outbreak of acute gastroenteritis among hospital staff who consumed food from the same restaurant?

Next Step in Outbreak Investigation

The next step is to conduct a case-control study to identify specific food items or exposures associated with illness (Option B). 1

Rationale for Case-Control Study

The outbreak has already been established with 15 of 50 hospital staff ill with similar symptoms and common restaurant exposure, completing the initial investigation phase. 1 The immediate priority is now to systematically identify which specific food items at the restaurant caused the outbreak through formal epidemiologic investigation. 1

Why Case-Control Study Takes Priority

• The CDC recommends conducting a formal case-control study to identify specific food items through systematic comparison of cases (ill staff) and controls (well staff who also ate at the restaurant). 1

• The case-control study quantifies the strength of association between suspected exposures and illness using odds ratios—historical outbreak investigations have identified associations with odds ratios as high as 84.0 for specific implicated foods, providing clear direction for targeted interventions. 1

• The WHO explicitly advises against delaying the case-control study to pursue environmental investigations first, as this wastes time and resources without epidemiologic direction. 1

Why Other Options Are Premature

Option A (Isolation) - Not the Immediate Priority

• The CDC indicates that isolation of affected individuals is not the immediate priority in a foodborne outbreak investigation where the source remains unidentified. 1

• Isolation becomes appropriate later for specific pathogens with person-to-person transmission concerns, but only after identifying the vehicle of infection. 1

Option C (Quarantine Restaurant Staff) - Premature Without Evidence

• The WHO states that quarantining restaurant staff without epidemiologic evidence identifying the specific food vehicle wastes time and resources. 1

• This determination comes after the case-control study identifies the implicated food and subsequent environmental investigation confirms the source. 1

Option D (Food Processing Data) - Comes After Case-Control Study

• Collecting detailed data about the restaurant's food processing is part of the subsequent environmental and laboratory investigation phase. 1

• This includes collecting samples of implicated foods for microbiologic testing and screening food handlers for infection, but only after the case-control study identifies which specific foods to investigate. 1

Practical Implementation Steps

• Define cases using clinical criteria (acute gastroenteritis with specific symptom onset timing) and identify controls from hospital staff who ate at the restaurant but remained well. 1

• Conduct structured interviews about all specific food items consumed at the restaurant, then calculate odds ratios for each food exposure to identify the vehicle of infection. 1

• Collect stool specimens immediately from at least 10 ill persons during the first 48 hours of illness, as viral diagnostic yield drops precipitously after 2-3 days when viral shedding decreases below detectable levels. 1

Subsequent Control Measures

After the case-control study identifies the implicated food:

• Exclude infected food handlers until stool cultures are negative. 1

• Provide food handler education on hygiene practices to prevent future outbreaks. 1

• Do not overlook asymptomatic food handlers, as they can be colonized and transmit infection without symptoms. 1