The correct answer is option 2, Influenza. Influenza, commonly known as the flu, is a respiratory illness caused by the influenza virus. The influenza virus is a highly contagious virus that spreads through respiratory droplets when an infected person coughs, sneezes, or talks. It can also be contracted by touching surfaces contaminated with the virus and then touching the face.

Option 1, Cholera, is not caused by a virus but by bacteria called Vibrio cholerae. Cholera is a waterborne disease that is typically spread through contaminated water or food.

Option 3, Scabies, is a skin infestation caused by the mite Sarcoptes scabiei. It is not caused by a virus.

Option 4, Typhoid, is caused by a bacterium called Salmonella typhi. It is a waterborne disease that is usually spread through contaminated food or water.

Therefore, it is clear that only option 2, Influenza, is caused by a virus.