What percentage of re-emerging diseases are zoonotic?

• A. 70%
• B. 50%
• C. 30%
• D. 10%

Answer: (A)

Most re-emerging infectious diseases come from animals, with spillover to humans driving many of these outbreaks. This reflects the widespread role of animal reservoirs and interfaces in the dynamics of disease return after a period of control. The figure around 70% captures a commonly cited estimate that a large majority of re-emerging infections are zoonotic, meaning they originate in animals before affecting people. This underlines why One Health approaches—integrated surveillance and collaboration across human, animal, and environmental health—are essential for anticipating and preventing these events. For example, outbreaks like SARS, MERS, Nipah, and various avian influenzas illustrate how pathogens at the animal–human boundary can reappear or re-emerge under changing ecological and social conditions. The other numbers would underestimate the extent to which animal hosts contribute to re-emerging diseases, which is why 70% is considered the best reflection of the pattern.