A 30-year-old male presented with complaints of sudden onset of fever, chills along with severe headache, backache and retro-orbital pain for 3 days. On 3rd day a rash appeared on the face, thorax and flexor surfaces. The rash was a macular confluent rash. Tourniquet test was positive. Lab findings revealed, Low platelet count Low WBC count Increased SGOT and SGPT levels Hematocrit increase by >20% The above disease is transmitted by which of the following vectors: –

**Core Concept**
The patient's symptoms and lab findings are indicative of a severe infectious disease characterized by fever, rash, thrombocytopenia, and elevated liver enzymes, suggesting a diagnosis of **Dengue Hemorrhagic Fever (DHF)**. This condition is caused by the dengue virus, transmitted primarily through the bite of an infected mosquito vector.

**Why the Correct Answer is Right**
The dengue virus is transmitted by the bite of an infected **Aedes mosquito**, particularly species such as _Aedes aegypti_ and _Aedes albopictus_. These mosquitoes are the primary vectors responsible for the spread of dengue fever, which can progress to DHF in severe cases. The virus is transmitted through the saliva of the infected mosquito, leading to symptoms such as fever, headache, and rash, as well as lab findings like thrombocytopenia and elevated liver enzymes.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as the patient's symptoms and lab findings do not suggest a diagnosis of Malaria, which is transmitted by the bite of an infected Anopheles mosquito.

**Option B:** Incorrect, as the patient's symptoms and lab findings do not suggest a diagnosis of Leptospirosis, which is transmitted through contact with contaminated water or soil.

**Option C:** Incorrect, as the patient's symptoms and lab findings do not suggest a diagnosis of Typhoid Fever, which is transmitted through contaminated food or water.

**Clinical Pearl / High-Yield Fact**
The tourniquet test, also known as the capillary fragility test, is a useful diagnostic tool for detecting dengue hemorrhagic fever, as it measures capillary fragility by observing the appearance of petechiae (small red or purple spots) on the skin after applying a tourniquet.

**Correct Answer:** .

✓ Correct Answer: C. <img style="max-width: 100%" src=" />