If a human disease breaks out across a large region of the world, what is it called?

Correct answer: (a) Pandemic

Explanation

A pandemic is an outbreak of infectious disease spread across a large region or the whole world, affecting a big share of the population.

An epidemic is confined to one area or country; when it spreads worldwide it becomes a pandemic (e.g. COVID-19, declared by WHO in 2020).

An endemic disease is constantly present in a region, while epizootic refers to disease outbreaks in animals.