The following is responsible for causing ophthalmia neonatorum on 5-7th day after bih: March 2013 (b)
**Core Concept**
Herpes Simplex Virus (HSV) type 2 is a common cause of ophthalmia neonatorum, a conjunctivitis that occurs in newborns. HSV-2 is primarily transmitted from mother to child during childbirth, resulting in the infection of the newborn's eyes.
**Why the Correct Answer is Right**
HSV-2 infection in newborns typically occurs 5-7 days after birth, which is consistent with the given timeframe. This is because the virus has time to replicate and cause symptoms after the initial exposure during delivery. HSV-2 infection leads to an acute conjunctivitis characterized by inflammation of the conjunctiva, which can progress to corneal ulcers and vision loss if left untreated. The virus enters the eye through the conjunctiva, causing an immune response that leads to the characteristic symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** Chemical conjunctivitis is a type of irritant contact conjunctivitis caused by exposure to chemicals, which is not typically associated with a 5-7 day timeframe after birth.
**Option C:** Neisseria gonorrhoeae is a common cause of ophthalmia neonatorum, but it typically presents within the first 24-48 hours after birth, not 5-7 days later.
**Option D:** Chlamydia trachomatis is another common cause of ophthalmia neonatorum, but it typically presents 5-14 days after birth, not within the 5-7 day timeframe specified in the question.
**Clinical Pearl / High-Yield Fact**
HSV-2 ophthalmia neonatorum is a medical emergency that requires prompt treatment with antiviral medications, such as acyclovir, to prevent vision loss and long-term complications.
**✓ Correct Answer: B. Herpes Simplex Virus II**