Acute haemorrhagic conjunctivitis is caused by
**Core Concept**
Acute haemorrhagic conjunctivitis (AHC) is a highly contagious and acute form of conjunctivitis characterized by sudden onset of pain, redness, and haemorrhages in the conjunctiva. It is primarily caused by viral infections, which lead to inflammation and congestion of the conjunctival blood vessels.
**Why the Correct Answer is Right**
The correct answer is caused by the enterovirus 70 (EV70) and coxsackievirus A24 variant (CA24v). These viruses are highly contagious and spread through direct contact with an infected person or through contaminated surfaces. The infection leads to inflammation of the conjunctiva, resulting in the characteristic symptoms of AHC, including pain, redness, and haemorrhages. The virus replicates in the conjunctival epithelial cells and causes damage to the blood vessels, leading to the characteristic haemorrhagic appearance.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because adenovirus is a common cause of acute conjunctivitis, but it is not typically associated with haemorrhages. Adenoviral conjunctivitis is usually characterized by watery discharge and a more gradual onset.
**Option B:** This option is incorrect because herpes simplex virus (HSV) causes a different form of conjunctivitis, known as herpetic keratoconjunctivitis, which is characterized by a more gradual onset and a vesicular rash on the conjunctiva.
**Option C:** This option is incorrect because chlamydial conjunctivitis is a form of inclusion conjunctivitis, which is typically associated with a more chronic course and a mucopurulent discharge.
**Clinical Pearl / High-Yield Fact**
AHC is highly contagious and can be spread through direct contact with an infected person or through contaminated surfaces. It is essential to practice good hygiene, including frequent handwashing and proper disinfection of surfaces, to prevent the spread of the infection.
**Correct Answer: D. Enterovirus 70 (EV70) and coxsackievirus A24 variant (CA24v)**