Carl Zimmer (YC ’87) begins Air-Borne as an audience member at the Skagit Valley Chorale’s May 2023 performance, imagining the drift of microscopic droplets—suspended particles carrying viruses and bacteria, exhaled and inhaled by all in the chorus. He then uses a carbon dioxide monitor to grasp this invisible exchange, tracking rising carbon dioxide concentrations in the air around him as a proxy for microscopic droplets.
While Air-Borne explores the weightless world of airborne microbes, what makes it exceptional is Zimmer’s ability, like a carbon dioxide monitor, to connect the invisible science with the real people who discover and live it.
In 2020, a Skagit Valley Chorale rehearsal became one of the first confirmed COVID-19 superspreader events in the US. At the time, scientists believed respiratory diseases spread mainly through droplets—heavy particles expelled when people cough or sneeze—which were thought to fall to the ground quickly and transmit infection only during close-range interactions. This understanding was reflected in official guidance from the World Health Organization, which recommended maintaining a minimum distance of one meter from others, especially those who were coughing, sneezing, or showing signs of illness
Zimmer follows a small group of scientists who worked to overturn this assumption, showing that COVID-19 could be spread not just through droplets but through the air itself, carried on tiny aerosol particles. In the case of the Skagit Valley Chorale, it could even be “spread on a song.”
The scientific battle to prove airborne transmission began long before COVID-19. Zimmer traces this scientific journey, highlighting pioneers like Louis Pasteur, Joseph Lister, and William and Mildred Wells, whose research helped piece together the invisible transmission pathways of infectious disease. He takes readers through the hidden microbial ecosystems that surround us, from microbial clouds in subway systems to bacteria-laden gusts of wind drifting through the skies, and even to battlefields, where the US and the Soviet Union experimented with the airborne spread of anthrax and smallpox as tools of biological warfare.
Zimmer’s reporting is both rigorous and poetic. He explains how airborne pathogens move, adapt, and impact our health, while also critiquing conventional public health messaging. He weaves science into story, showing how a better understanding of airborne transmission could have prevented the “failure of imagination” that delayed early pandemic responses.
Air-Borne reveals the wonder of the unseen world—the “gaseous ocean in which we all live, which infiltrates our bodies, which our own bodies transform and then return to the great transparent sea, that contains exhaled viruses that can then be inhaled.” His exploration of airborne life lingers in the imagination long after the final page, much like the unseen particles that surround us—ever-present, shaping every breath we take.