## Core Concept
The International Health Regulations (IHR) are an international legal instrument that is binding on 196 countries across the globe, including all the Member States of WHO. The purpose of IHR is to prevent, protect against, control, and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade. Under the IHR, countries are required to report certain diseases that could pose a public health emergency of international concern (PHEIC).

## Why the Correct Answer is Right
The correct answer, **Yellow Fever**, is one of the diseases that come under international surveillance due to its potential to cause significant public health emergencies. Yellow fever is a viral disease transmitted by infected mosquitoes and can lead to severe illness, including hemorrhagic fever and death. Because of its high mortality rate and potential for spread across international borders, it is closely monitored.

## Why Each Wrong Option is Incorrect
- **Option A:** While several diseases can cause significant public health concerns, without specifying what disease A represents, it's difficult to directly refute its inclusion. However, diseases under international surveillance typically have specific characteristics like high contagiousness, high mortality rates, or potential for rapid spread.
- **Option B:** Similarly, without specifics on disease B, a direct refutation isn't feasible. Generally, diseases under surveillance have a significant impact on public health and can spread across borders.
- **Option D:** Disease D's characteristics are unknown, making direct refutation challenging. The focus on international surveillance typically includes diseases with epidemic potential.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **Yellow Fever** vaccination is actually one of the requirements for international travel to certain countries in endemic areas, as stipulated by the International Health Regulations. This is a critical piece of information for travelers and clinicians alike, highlighting the importance of vaccination in preventing the spread of this disease.

## Correct Answer: C. Yellow Fever