Throughout history we have been faced with plagues and epidemics –outbreaks of diseases that spread quickly and affect many people at the same time.
Our hunter and gatherer ancestors lived in small groups, limited perhaps to 30-60 individuals. They did not travel far, and they lived in self-sufficient communities with limited infections and no epidemics. If a contagious infection impacted one of these small communities, the disease would either kill off the entire population, or some would die and others would be immune. Sometimes, a pathogen was latent, which meant that it might infect one generation, and then skip a generation. But, because of the small size of the community, the pathogen had no place else to go and so it would often die out. Fast forward to present day, Homo Sapians evolved and we learned to travel, increase trade across continents, and build grand cities with dense populations. We stored food in our homes, which attracted rodents, and hungry pests. And we started to see true plagues and epidemics escalate, killing millions of people.
We have learned that the “plague” in its most common reference is caused by a bacterium called Yersinia pestis that often infects rats, mice, squirrels and other small rodents and is usually transmitted to humans through the bite of an infected flea. Tuberculosis is also a plague – caused by another bacillus. One of the first documented plagues was the Justinian Plague in 541 AD. This plague, named after then Byzantine emperor Justinian I, likely originated in Africa and then spread to Europe through infected rats on merchant ships, killing as many as 10,000 people per day, and claiming as many as 100 million deaths.
The second pandemic, commonly called the “Black Death” (or Great Plague) originated in China in the 1330’s, peaked in 1347 and spread across Europe, wiping out entire towns. The Great Plague finally ended around 1353, but not before killing an estimated 50 million people and more than half the population of Europe at the time.
Other more modern epidemics include the 1918 Flu (20+ million deaths); the Modern Plague, 1894-1903 (10 million deaths); HIV/AIDS 1960-present (39 million deaths) and Asian Flu, 1957-1958 (2 million deaths).
Today we have better hygiene, cleaner public water systems and we have developed vaccines and antibiotics to fight off many of these pathogens.
But new infectious pathogens are being discovered every day. Large farms are one of the biggest risks because of the constant contact between animals and people. And low dose antibiotics in large scale animal agriculture has contributed to increased antibiotic resistance in our bodies. With increased globalization we should be very careful what we eat and where we go to source our food.