Throughout human history, we have been in a continuous battle for survival with bacteria, viruses and fungi that live in the environment and inside our bodies. History has been filled and shaped by infectious disease outbreaks that have killed more people than war or natural disasters – from the plague in the Middle Ages, to cholera in 19th century, to flu in the early 20th century and now the evolving COVID-19 pandemic.
But many humans have become complacent and forgotten this history.
In the 20th century, scientists and the medical profession tamed most of the dangerous microbes of previous centuries, with improvements in sanitation, hygiene, animal and pest control. Further, the discovery of antibiotics and the implementation of childhood vaccine programs sharply reduced infectious disease deaths globally. While pneumonia, tuberculosis, and diphtheria were among the top causes of death in 1900, by 2014, non-infectious diseases like heart disease, cancer, and strokes were the top killers.
But pathogens were quietly learning to adapt during this time too.