Which of the following is a viral disease?

Options

A. Typhoid
B. Polio
C. TB
D. Leprosy

Explanation

To determine which of the following is a viral disease, we will analyze each option provided:

1. **Typhoid**: This disease is caused by the bacterium *Salmonella typhi*. Therefore, it is not a viral disease.

2. **Polio**: This disease is caused by the poliovirus. Since it is caused by a virus, it is classified as a viral disease.

3. **TB (Tuberculosis)**: This disease is caused by the bacterium *Mycobacterium tuberculosis*. Hence, it is not a viral disease.

4. **Leprosy**: This disease is caused by the bacterium *Mycobacterium leprae*. Therefore, it is also not a viral disease.

Based on the analysis, the only viral disease among the options provided is **Polio**.

### Final Answer:
**Polio** is a viral disease.

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