Which statement about outbreaks is true?

• A. A pseudo-outbreak is an increase in positive cultures or tests without clinical disease.
• B. Outbreaks can only occur in areas under surveillance in a facility.
• C. A cluster is not considered an outbreak.
• D. A single case of an unusual disease does not constitute an outbreak.

Answer: (A)

Understanding outbreaks involves telling apart a real surge in disease from an apparent rise in test results that doesn’t reflect illness, known as a pseudo-outbreak. A pseudo-outbreak describes an increase in positive cultures or tests without actual clinical disease among patients, often caused by lab errors, specimen contamination, mislabeling, or other data artifacts. This distinction matters because the right response depends on whether people are truly affected or just the data suggest otherwise. When you encounter a spike in positives, you look for clinical illness in patients, review how samples were collected and processed, check for contamination or instrument issues, and consider repeating tests to confirm results. If there’s no accompanying illness and no epidemiologic link, you’re dealing with a pseudo-outbreak rather than a true outbreak.

The other statements don’t fit because outbreaks aren’t limited to areas under surveillance, and a cluster can indeed be part of or the lead-in to an outbreak investigation. Also, while a single case of an unusual disease often prompts careful review, outbreaks are generally characterized by a higher-than-expected number of cases rather than just one, though rare exceptions exist depending on the disease and context.