Epidemiological patterns refer to the occurrence of disease events according to a parameter such as time, place, or population. These different patterns allow us to broadly observe the impact of disease and trace its course.
These patterns help epidemiologists understand the spread of the disease, for example, and this understanding guides interventions. Epidemiological patterns also tell us how fast and far a disease is spreading, allowing us to evaluate the level of danger it poses to our species as a whole.
There have been many widespread diseases in the past that have wiped a large chunk of the human population off the face of the earth. The Black Death, influenza, and COVID-19 are a few examples. Pathogens that spread rapidly from one host to another, infecting entire populations in a short time, raise such alarms.
However, complete host extinction is hindered by the dependence of the pathogens on the hosts to reproduce and spread. As the disease spreads, healthy individuals decrease, lessening the opportunity for the pathogen to spread as rapidly. This is a self-limiting property of pathogens’ complex relationship with their hosts.
Even the deadliest of diseases leave a portion of the population unharmed due to the self-limiting model of pathogens. The outcomes of many pandemics are devastating, but host extinction is not achieved even with such massive destruction.