The Andes hantavirus outbreak shows how easily disease labels are misunderstood — and why they describe patterns of spread, not how dangerous a virus is.
The recent outbreak of the rare Andes hantavirus has once again drawn attention to terms that became widely familiar during the COVID‑19 pandemic: endemic, epidemic and pandemic.
These concepts are often grouped together or misused in public discourse, but in epidemiology they have precise meanings. Importantly, they describe how a disease spreads — not how dangerous it is. So what do the terms actually mean?
A disease that occurs regularly in certain regions is called endemic. When a disease becomes endemic, the number of people falling ill remains relatively constant over time.
The number of cases is higher than in other areas but does not increase over time. Over a certain period of time, approximately the same number of people repeatedly contract the disease.
