**Question:** Vector control for yellow fever around an airport is done upto a distance of-

A. 10 km
B. 20 km
C. 30 km
D. 50 km

**Core Concept:** Yellow fever is a viral hemorrhagic fever caused by the yellow fever virus, primarily transmitted to humans through the bite of infected Aedes species mosquitoes. Aedes species mosquitoes breed in man-made containers, especially around airports, and are effectively controlled within a specific distance from the airport.

**Why the Correct Answer is Right:** The correct answer, D. 50 km, represents the effective range of vector control around an airport for yellow fever prevention. This is because the primary vectors, Aedes species mosquitoes, breed in man-made containers near airports, and the control measures are mainly focused within a radius of 50 kilometers to effectively reduce the risk of yellow fever transmission.

**Why Each Wrong Option is Incorrect:**

A. 10 km: This is too short a distance as Aedes mosquitoes can breed over a broader range, making it less effective in controlling the transmission of yellow fever.

B. 20 km: Although Aedes mosquitoes can breed within 20 km, the range is still too narrow compared to the actual effective control radius.

C. 30 km: Similar to option B, this distance is too narrow for comprehensive vector control, as Aedes mosquitoes can breed further than 30 km.

**Why the Correct Answer is Right:**

**Clinical Pearl:** Yellow fever is a mosquito-borne viral disease that can be prevented by controlling the mosquito vectors, particularly Aedes species mosquitoes, within a radius of around 50 km from airports. Effective vector control measures, such as larval source management and adult mosquito control, are essential around airports to minimize the risk of yellow fever transmission.