Primary Step in Rotavirus Outbreak Investigation
After laboratory confirmation of rotavirus in stool samples, the primary step in outbreak investigation is interviewing patients to characterize the clinical and epidemiological features of the outbreak. 1
Why Patient Interviews Come First
CDC guidelines explicitly state that epidemiologic investigation should proceed immediately once an outbreak is recognized, even when laboratory confirmation has already been obtained. 1 The question specifies that rotavirus has already been confirmed in stool samples, making additional confirmatory testing unnecessary at this stage.
Laboratory confirmation is already complete in this scenario—the virus has been identified in stool samples. 1 Additional confirmatory testing is only warranted when the diagnosis would be unusual (such as rotavirus in adults or children during summer months), which is not indicated here. 2
Critical Information to Gather During Patient Interviews
Patient interviews must systematically establish the outbreak parameters: 1
- Timing of symptom onset to construct an epidemic curve that reveals the outbreak's progression
- Common exposures among affected individuals (shared food, water sources, locations, or fomites like toys) 3
- Clinical characteristics including severity, duration, and specific symptoms
- Attack rates among different demographic groups to identify high-risk populations
- Demographic data to characterize who is affected
The Systematic Investigation Sequence
The CDC-recommended outbreak investigation follows this algorithmic approach: 1
- Interview patients and characterize the outbreak (primary step after confirmation)
- Develop hypotheses about source and transmission based on interview data
- Test hypotheses through additional targeted investigation
- Implement or enhance control measures based on findings
- Continue surveillance to monitor outbreak resolution
Why Other Options Are Not Primary
Option A (Confirm samples with lab): Already completed—the question states rotavirus has been confirmed in stool samples. 1
Option C (Develop hypothesis about source): This comes after patient interviews, as hypotheses must be based on epidemiologic data gathered from interviews. 1 You cannot develop evidence-based hypotheses without first characterizing the outbreak through patient interviews.
Option D (Activate immediate health precautions): Standard infection control measures should already be in place for hospitalized patients with confirmed rotavirus (contact precautions with gowns, gloves, strict handwashing, and separation of ill from well persons). 1 These are baseline measures, not the primary investigative step.
Common Pitfalls to Avoid
Do not delay patient interviews to conduct additional laboratory testing when rotavirus has already been confirmed. 1 The CDC recommends collecting specimens from at least 10 ill persons during outbreaks, but this is for initial diagnosis, not after confirmation. 1
Do not assume you know the source without epidemiologic data. Rotavirus can be transmitted through multiple routes including person-to-person contact, contaminated food 4, and fomites such as shared toys. 3 Only systematic patient interviews will reveal the specific transmission pattern in your outbreak.
Specimens must be collected within 48 hours of illness onset if additional testing is needed, as viral shedding drops below detectable levels after 2-3 days. 5
The answer is B: Interviewing the patient and their symptoms is the primary step in outbreak investigation after laboratory confirmation.