The idea that pandemics occur roughly every 100 years is a generalization rather than a precise rule. While there have been significant pandemics throughout history, their timing and severity vary greatly. Some pandemics have occurred within decades of each other, while others have been separated by centuries.


One reason for the perception of a roughly 100-year cycle might be due to some of the most significant pandemics in recent history:


1. **The Spanish flu (1918-1919)**: This was one of the deadliest pandemics in history, causing an estimated 50 million deaths worldwide. It occurred around a century ago and is often cited as an example of a major pandemic.


2. **COVID-19 pandemic (2019-present)**: This ongoing pandemic has affected the world profoundly, with millions of deaths and significant societal and economic impacts. It's also close to the century mark from the Spanish flu pandemic, contributing to the perception of a 100-year cycle.


However, it's essential to note that pandemics can occur at any time and are influenced by various factors such as population density, global travel, urbanization, environmental changes, and the emergence of new pathogens. Additionally, advances in healthcare, public health measures, and technology can impact the spread and severity of pandemics, making it challenging to predict their occurrence with precision.


While historical patterns can provide insights into pandemic dynamics, it's crucial to approach such generalizations with caution and recognize the complexity and variability of infectious disease outbreaks.