If a naturally occurring disease requires a vector for spread and the competent vector is missing, this is an example of which clue?

• A. Common disease
• B. Uncommon disease
• C. Rare outbreak
• D. Endemic disease

Answer: (B)

The main idea is how relying on a vector to spread a disease affects how often you’d expect to see it. If the competent vector is missing, transmission drops and the disease won’t spread readily, so its occurrence is not frequent. That makes it an uncommon disease under these conditions. A common disease would still spread easily even without noting a missing vector, which isn’t the case here. A rare outbreak describes a sudden, unusual spike in cases rather than a consistent pattern tied to the absence of the vector. An endemic disease is one that normally maintains a baseline level in a population; without the vector, that regular transmission would be disrupted, not characterizing the illness as endemic. So the scenario best fits an uncommon disease.