**Core Concept**
Acute Flaccid Paralysis (AFP) is a condition characterized by the sudden onset of muscle weakness or paralysis, which can be caused by various underlying conditions, including infectious, inflammatory, and metabolic disorders. The causes of AFP can be broadly categorized into poliomyelitis, non-polio enteroviral infections, and other etiologies.

**Why the Correct Answer is Right**
Poliovirus is a highly infectious agent that causes poliomyelitis, a leading cause of AFP worldwide. The virus primarily affects the motor neurons in the spinal cord, resulting in muscle weakness or paralysis. The poliovirus replicates in the gut and then invades the central nervous system, leading to the characteristic symptoms of AFP.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it is not a recognized cause of AFP. However, other enteroviruses like Coxsackievirus and Echovirus can cause AFP, but they are not as common as poliovirus.
* **Option B:** This option is incorrect as it is not a direct cause of AFP. While Guillain-Barré Syndrome (GBS) can present with similar symptoms, it is an autoimmune disorder that typically follows an antecedent infection, such as a gastrointestinal or respiratory illness.
* **Option C:** This option is incorrect as it is not a recognized cause of AFP. However, other viral infections like West Nile Virus and Zika Virus can cause neurological symptoms, but they are not typically associated with AFP.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that AFP can be caused by various underlying conditions, and a prompt diagnosis is crucial to initiate appropriate treatment and prevent long-term sequelae. In areas where polio is endemic, AFP cases should be reported to the local health authorities immediately.

**Correct Answer: A. Poliovirus**