What is the next step in managing an outbreak of acute gastroenteritis among hospital staff who all had food from the same restaurant before symptoms appeared?

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 investigation has already completed its initial phase—establishing that an outbreak exists with 15 of 50 staff ill with similar symptoms and common restaurant exposure. 1 The current phase requires systematic epidemiologic investigation before pursuing environmental or control measures.

• The CDC explicitly recommends conducting a formal case-control study to identify specific food items through systematic comparison of cases and controls, rather than pursuing environmental investigations first. 1
• The WHO warns against delaying the case-control study to pursue environmental investigations without epidemiologic direction, as this wastes time and resources. 1
• Historical outbreak data demonstrates that structured interviews calculating odds ratios for each food exposure can identify associations as high as 84.0 for specific implicated foods (as seen in the Connecticut Department of Public Health investigation with potato salad), which then guides targeted interventions. 1

Why Other Options Are Premature

Isolation of affected individuals (Option A) is not the immediate priority when the source remains unidentified, and would be appropriate later only for specific pathogens with person-to-person transmission concerns. 1

Quarantining restaurant staff (Option C) without epidemiologic evidence identifying the specific food vehicle wastes time and resources—this determination comes after the case-control study identifies the implicated food and subsequent environmental investigation. 1

Collecting detailed data about food processing (Option D) represents the environmental investigation phase, which should follow rather than precede the case-control study to avoid wasting resources without epidemiologic direction. 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
• Store bulk diarrheal specimens at +4°C rather than frozen to preserve viral morphology for electron microscopy. 1

Subsequent Actions After Case-Control Study

Once the case-control study identifies the implicated food, the subsequent phase involves environmental and laboratory investigation, including collecting samples of implicated foods for microbiologic testing and screening food handlers for infection. 1 Food handlers should be excluded until stool cultures are negative, and education on hygiene practices should be provided to prevent future outbreaks. 1

Critical Pitfall to Avoid

Do not assume all restaurant exposures are equal—the case-control study is essential to identify specific high-risk items rather than implementing broad, unfocused interventions. 1 Research demonstrates that even asymptomatic food handlers can be colonized and transmit infection, and viral shedding can continue up to 10 days after illness resolution. 1, 2