Based on a ranking of major epidemics and pandemics by their estimated death tolls, the disease associated with the top-ranked event is Influenza A/H1N1, which caused the Spanish Flu pandemic.
The Spanish Flu, an influenza pandemic that swept the globe from 1918 to 1920, is identified as the single deadliest event in the provided ranking of historical outbreaks.
Here is a partial overview of some major epidemics and pandemics and their associated diseases, ranked by death toll:
| Rank | Epidemics/Pandemics | Disease |
|---|---|---|
| 1 | Spanish flu | Influenza A/H1N1 |
| 2 | Plague of Justinian | Bubonic plague |
| 3 | HIV/AIDS pandemic | HIV/AIDS |
| 4 | Black Death | Bubonic plague |
While some diseases, such as Bubonic Plague, have caused multiple distinct pandemics throughout history—including the Plague of Justinian and the Black Death, both listed above—leading to substantial cumulative death tolls over time, the ranking focuses on individual, major epidemic or pandemic events. Within this context, the Spanish Flu stands as the deadliest listed event.
