**Core Concept**
Mosquito-borne infectious diseases are a significant public health concern worldwide. The primary vectors for these diseases are various mosquito species, which transmit pathogens through their saliva during feeding. Understanding the role of mosquitoes in disease transmission is crucial for prevention and control measures.

**Why the Correct Answer is Right**
Yellow fever is a viral hemorrhagic fever caused by the yellow fever virus (YFV), which is transmitted primarily through the bite of an infected female Aedes mosquito. The virus is maintained in a cycle between the mosquito and non-human primates. When an infected mosquito bites a human, it can transmit the virus, leading to the disease. The Aedes mosquito species, particularly Aedes aegypti, is responsible for the majority of yellow fever cases.

**Why Each Wrong Option is Incorrect**
**Option A:** Hepatitis A is primarily spread through the fecal-oral route, often through contaminated food or water, and is not transmitted by mosquitoes.

**Option B:** Cholera is caused by Vibrio cholerae and is usually spread through contaminated food or water. While mosquitoes can transmit diseases, they are not the primary vectors for cholera.

**Option D:** Leprosy, caused by Mycobacterium leprae, is primarily spread through close contact with an infected person, and mosquitoes are not involved in its transmission.

**Clinical Pearl / High-Yield Fact**
Remember that mosquitoes are the primary vectors for several important diseases, including yellow fever, dengue fever, Zika virus, and chikungunya. Understanding the role of mosquitoes in disease transmission is crucial for implementing effective prevention and control measures.

**✓ Correct Answer: C. Yellow fever**