**Core Concept**
Tetanus is a bacterial infection caused by Clostridium tetani, characterized by muscle stiffness and spasms. The bacterium produces tetanospasmin, a potent neurotoxin that disrupts neurotransmitter release, leading to the characteristic symptoms of tetanus.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of tetanus. Tetanospasmin, the neurotoxin produced by C. tetani, inhibits the release of neurotransmitters such as glycine and GABA, which are involved in inhibitory neurotransmission. This results in an imbalance between excitatory and inhibitory neurotransmission, leading to muscle stiffness and spasms. The toxin also affects the spinal cord, causing the characteristic rigidity and spasms associated with tetanus.

**Why Each Wrong Option is Incorrect**
**Option A:** Tetanus is caused by a viral infection. **Incorrect** because tetanus is a bacterial infection caused by Clostridium tetani, not a viral infection.
**Option B:** Tetanus is treated with antibiotics only. **Incorrect** because while antibiotics may be used to treat tetanus, the primary treatment involves administration of tetanus immunoglobulin and wound care to prevent further toxin release.
**Option C:** Tetanus toxin affects the peripheral nerves. **Incorrect** because tetanus toxin primarily affects the spinal cord, causing the characteristic rigidity and spasms associated with tetanus.

**Clinical Pearl / High-Yield Fact**
It is essential to administer tetanus immunoglobulin and wound care promptly in cases of suspected tetanus exposure to prevent the onset of symptoms. Tetanus immunoglobulin provides immediate protection against the toxin, while wound care helps prevent further toxin release.

**Correct Answer:** A.