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Introduction

What is the greatest contribution that medicine has made to humanity? In 2007, more than 11,000 readers of theBritish Medical Journal were surveyed to answer that question. The answers were (in order): (i) public health sanitation; (ii) discovery of antibiotics; (iii) discovery of anesthesia; (iv) discovery of vaccination; (v) discovery of the structure of DNA; and (vi) discovery of the germ theory of disease(1). Of the greatest contributions ever made to medicine, four of the top six were either the discovery of the germ theory of disease or innovations that were a direct result of that discovery. While the answers to this provocative question can be argued, the germ theory remains one of the most important contributions in the 2,500‐year history of Western medicine and a relatively recent one—only 150 years old.

Modern society has taken for granted the value of public health sanitation; the vanishing of vaccine‐preventable diseases such as smallpox, measles, and polio; and the existence of antibiotics to treat infectious diseases. In the 1970s, we even had the hubris to declare infectious diseases “conquered.” However, infectious diseases have emerged or reemerged to devastate our modern world. I didn’t realize when I made my decision to go into the specialty of infectious diseases in 1978, my last year of medical school, that I would be witness to this emergence. I thought that antibiotic treatments could actually cure people, not just treat them. Unlike chronic illnesses such as diabetes, bacterial pneumonia or a urinary tract infection, once treated with antibiotics, could be cured. I was not alone in this thinking.

I entered the specialty at a time when it was believed that medical science had nearly done it all—that there would be little left to do since we had such powerful agents for treating and curing infectious diseases. I recall my first meeting of the Infectious Diseases Society of America in 1981, when one of the foremost authorities in the field told the audience that “all infectious disease doctors would be doing in the next decade would be culturing each other.” This complacency would be short‐lived; such complacency has always been short‐lived in medicine. During the same meeting, James Curran, at the time working at the Centers for Disease Control (CDC) and now recently retired as dean of the Rollins School of Public Health at Emory University, was scheduled to describe the first cases of what would soon be called AIDS (acquired immunodeficiency syndrome). Curran was the last of four speakers in a session that began with 150 people in the audience. But word of these cases had spread through the conference. By the time Curran spoke, over 1,000 people had crammed into a room at a downtown hotel in Chicago, IL. Even though the attendees at the meeting were told that infectious diseases were “conquered,” the infectious disease community of doctors, microbiologists, and public health officials had clearly recognized that something new was happening.

Many new diseases, such as AIDS, hepatitis C virus, hantavirus, SARS (severe acute respiratory syndrome), MERS (Middle East respiratory syndrome), Zika, and COVID‐19 infection, have been described in the last 40 years. The microorganisms that cause these diseases were not actually new—they clearly existed before medical science became aware of them. In some cases, new techniques were developed to identify organisms that had always been there but that we could not detect. More often, the novelty for man