In a rotavirus gastroenteritis outbreak affecting 15 children, after laboratory confirmation and reporting to the health ministry, what is the first step in the outbreak investigation?

Primary Step in Rotavirus Outbreak Investigation

The primary step in investigating this confirmed rotavirus outbreak is to interview the patients and document their symptoms, exposure history, and epidemiologic characteristics to establish the outbreak's scope and transmission patterns. 1, 2

Why Patient Interviews Come First

The CDC guidelines explicitly emphasize that epidemiologic investigation should proceed immediately once an outbreak is recognized, even when laboratory confirmation has already been obtained. 2 Since you already have confirmed rotavirus in stool samples from 15 children, additional laboratory confirmation (Option A) is unnecessary and would delay critical outbreak control measures. 2

Interviewing patients must precede hypothesis development because you cannot formulate meaningful hypotheses about the source and transmission routes without first collecting detailed exposure histories and understanding the temporal and geographic distribution of cases. 1 Attempting to develop a hypothesis (Option C) before gathering this foundational epidemiologic data would be premature and potentially misleading. 1

Critical Information to Collect During Patient Interviews

The investigation should systematically gather: 2

• Timing of symptom onset to construct an epidemic curve and identify the incubation period (approximately 2 days for rotavirus) 1
• Clinical characteristics including vomiting duration (typically 3 days), watery diarrhea duration (3-8 days), fever, and abdominal pain 1
• Exposure history including day-care attendance, hospital stays, and contact with other ill children 1
• Common exposures between cases to identify potential transmission routes 2
• Attack rates among different groups to identify high-risk populations 2

Why Immediate Health Precautions Are Not the Primary Step

While infection control measures (Option D) are important, standard contact precautions with gowns, gloves, and strict handwashing should already be in place for hospitalized patients with confirmed rotavirus. 2 The primary investigative step is to characterize the outbreak through patient interviews, which will then inform targeted control measures based on identified transmission patterns. 1, 2

High-Risk Settings to Investigate Through Interviews

Patient interviews should specifically explore: 1

• Nosocomial transmission - all children hospitalized >2 weeks during rotavirus season may ultimately shed virus 1
• Day-care centers - both endemic and outbreak forms are common in these settings 1
• Neonatal units - outbreaks frequently occur, though full-term infants may have milder disease 1

Critical Pitfall to Avoid

Do not overlook asymptomatic transmission - approximately 50% of children shed rotavirus the day before diarrhea starts, and one-third continue shedding during the week after symptoms end. 1 This makes exposure history particularly important, as symptomatic cases alone will not reveal the full transmission chain.

The Systematic Investigation Sequence

After interviewing patients, the CDC recommends: 2

1. Developing hypotheses about source and transmission based on interview data
2. Testing hypotheses through additional targeted investigation
3. Implementing or enhancing control measures based on findings
4. Continuing surveillance to monitor outbreak resolution

Answer: B - Interviewing the patients and their symptoms