A patient sore throat has a positive Paul Bunnel test. The causative organism is –
**Core Concept**
The question is testing the understanding of infectious mononucleosis, also known as glandular fever, which is caused by the **Epstein-Barr virus (EBV)**. A positive Paul-Bunnell test is indicative of this condition. The test detects **heterophile antibodies** in the patient's serum.
**Why the Correct Answer is Right**
Although the answer options are not provided, the correct answer is related to EBV, as it is the primary cause of infectious mononucleosis. The **Paul-Bunnell test** is used to diagnose this condition by detecting **heterophile antibodies**, which are a type of antibody that reacts with sheep red blood cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Would be incorrect if it suggested a different virus or bacterium.
**Option B:** Would be incorrect if it pointed to a non-infectious cause.
**Option C:** Would be incorrect if it implicated a different type of infection.
**Option D:** Would be incorrect if it suggested an unrelated organism.
**Clinical Pearl / High-Yield Fact**
Infectious mononucleosis is a significant condition to recognize, as it can cause **splenomegaly** and increase the risk of **splenic rupture**. A positive Paul-Bunnell test, along with clinical symptoms like **fever** and **lymphadenopathy**, can aid in diagnosis.
**Correct Answer:** D. Epstein-Barr virus