Infections can change the trajectory of a life – and not always in for the worse. Patsy Cline, the celebrated country music singer, attributed her remarkable voice to an infection. “In childhood,” she said, “I developed a serious throat infection, and my heart stopped beating. I recovered from that illness with a voice that boomed forth like Kate Smith's!”
But bad viruses, bacteria, parasites, and fungi usually cause illnesses that are unwelcome. And when pathogens become widespread and unchecked, which they have proven they can do, time and again, they shape human history.
During the Black Death of the 14th Century, an estimated 25–50 million people in Europe died from bubonic plague. In the 18th Century, smallpox killed around 60 million. Fast forward to the 20th and 21st centuries, and we see the devastating effects of the Spanish Flu, HIV/AIDS, and COVID-19. Make no mistake about it, viruses hold the power to kill without mercy, disrupt our world, and bring health systems to their knees.
For centuries, nobody knew what caused infection. Divine punishment was the general consensus. It wasn’t until the mid-19th century that a clearer understanding began to emerge. Hungarian physician Ignaz Semmelweis was one of the first to observe that something invisible—what we now know were microbes—was transmitting disease. He famously reduced maternal deaths in childbirth by introducing simple handwashing with chlorinated lime. His ideas were dismissed at the time, but he was right.