What is a zoonosis?

• A. Diseases that can be passed from animals to humans and humans to animals.
• B. Diseases that occur only in humans.
• C. Diseases caused by viruses only.
• D. Diseases transmitted exclusively by insects.

Answer: (A)

Zoonosis means a disease that can be transmitted between animals and humans. The key idea is cross-species transmission—the illness can move from animals to people and, in some cases, from people back to animals. Pathogens involved can be viruses, bacteria, parasites, or fungi, so it’s not limited to viruses. It’s also not confined to transmission by insects; many zoonoses spread through direct contact with animals, contaminated food or water, or other routes. This definition explains why the concept fits best: the disease originates in animals and has the potential to affect humans as well. For example, rabies is a classic zoonosis transmitted through animal bites, while other zoonoses can come from contaminated animal products or environments.