covid!--4/22/2026

22 Apr 2026

covid!--4/22/2026

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Today's selection-- from Air-Borne by Carl Zimmer. The airborne transmission of disease:

“Two weeks after the March 10 rehearsal, the World Health Organization swatted down that notion. On their Twitter account, the agency wrote:

"FACT: #COVID19 is NOT airborne.

"The #coronavirus is mainly transmitted through droplets generated when an infected person coughs, sneezes or speaks.

"To protect yourself:

"keep 1m distance from others
disinfect surfaces frequently
wash/rub your 👐
avoid touching your 👁️👃👄

"The day after that tweet, the Skagit Valley Chorale outbreak became international news. A story in the Los Angeles Times drew the world's attention to the singing group nestled in a valley that wasn't known for much besides an annual tulip festival. CNN interviewed Burdick about the experience. Strangers sent a blast of hate mail. They said the singers had blood on their hands.

"The first lesson people took from the Skagit Valley Chorale outbreak was just how easily one person could infect many others. But in the months that followed, Ruth Backlund and her fellow survivors agreed to collaborate on a scientific study that helped establish something just as important. Contrary to what WHO claimed, the study concluded Covid-19 was airborne.

“I am a journalist, and diseases are one of my beats. I became aware of the new virus in early January 2020, while it was still in China. By late January, a few scientists were predicting a pandemic. I started warning my friends to brace for a possible disaster. Like a paranoid doomsday prepper, I advised them to store extra toilet paper and canned food. When someone called me to plan a meeting in June, I told him meetings might not exist in June.

“I was right in some ways and very wrong in others. Like the Skagit Valley Chorale, I did not concern myself with the air. If I stayed a few feet away from strangers, I'd be safe from any viruses they coughed or sneezed. The droplets they expelled would fall to the floor like ball bearings. The most worrisome risk seemed to lurk on surfaces: the skin of my hands, which I washed many times a day; the grocery bags that I disinfected with Clorox wipes.

“Over the following months, I absorbed the growing consensus that Covid-19 was in fact airborne. As I recognized that floating droplets could transmit the virus from one person to another, I traded Clorox wipes for a carbon dioxide monitor. Masks became a staple. I also began to think about the air differently, as a 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. But I was also left with a question: how could such a fundamental mystery about the worst public health disaster in a century go unsolved for so long?

Common measures implemented to prevent the spread of the virus

“Once the pandemic passed its peak-after most people on Earth got infected, vaccinated, or both-I started looking for an answer. It became clear that for thousands of years the atmosphere had been an intimate, enveloping mystery. For hundreds of generations, scholars and physicians had claimed the air itself could turn dangerous. They gave bad air an assortment of names, such as miasma. Miasmas could be caused by the stars or swamps; they could spread down a street or float for hundreds of miles. When modern Western medicine took shape in the late 1800s, scientists and doctors alike tossed miasmas aside, treating them like an embarrassing relic of the Dark Ages, a concept with as much value to medicine as bleeding patients. They knew that germs spread diseases, and they knew that germs spread primarily through food, water, sex, and touch, as well as through coughs and sneezes. Germs were not airborne.

“But in the 1930s, a few scientists challenged this consensus. They argued that diseases could indeed spread on currents, that germs could float for hours like smoke. They recognized that airborne pathogens posed a fundamentally different threat than the one posed by short-range coughs and sneezes. They argued that some of the worst diseases known to humanity, such as tuberculosis and influenza, spread this way. Those scientists helped create a new field: the science of airborne life. They called it aerobiology.

“The aerobiologists were a motley crew. As some tracked pathogens floating inside schools and subways, others caught microbes soaring through the sky. They dazzled the world by finding spores as high as the stratosphere. The founders of aerobiology hoped their new science would unify all life of the air, whether indoors or outdoors, and make clear that the airborne diseases that afflict us are just a few species among a vast floating menagerie.

“Today, aerobiologists look at the atmosphere as one of the three great habitats of life. It didn't start out that way: when the Earth formed 4.7 billion years ago, a blanket of lifeless air formed from the gases hissing out of the molten planet. Life started off aquatic–some theories point to the young ocean as its nursery, others to freshwater ponds–but it did not stay restricted to water for long. Waves sprayed droplets containing bacteria and viruses into the air. About 2 billion years ago, the ancestors of algae and other single-celled forms of life also leaped from the water and traveled for hundreds or thousands of miles.

“When life spread to land, the air filled with new species. The winds scattered mats of terrestrial microbes, and then plants and fungi began releasing spores into the wind. Later, some plants evolved flowers that released pollen grains. Their airborne journeys became part of the recipe for their enormous evolutionary success. The greening land also lured animals ashore. To get their oxygen, they adapted to breathing air rather than pumping water through gills. And then some animals–insects first, then birds and bats–evolved to move through the air, with leaping legs and flapping wings.

“The animals became, in turn, hosts to another kind of airborne life: pathogens that floated from one host to another. Hantaviruses, for instance, infect rodents and then escape in their urine and saliva. On the ground they can survive in dried dust. Days later, a breeze can pick up hantaviruses and carry them into the nose of another rodent visiting the same spot, causing a fresh infection.

“Other pathogens turned the lungs of air-breathing animals into both a home and a launching pad. They get drawn into a host with an inhaled breath. Animals often react to a respiratory infection with an onslaught of immune cells and inflammation. This attack leaves an extra supply of mucus in the airway. To clear it out, the animals will use their lungs to deliver a powerful cough or sneeze. The contaminated mucus droplets can then strike other animals or contaminate the ground. But even regular breathing can be enough to spread some microbes. When an animal exhales air, the outgoing flow pulls droplets off the moist walls of the lungs, like a breeze passing over the ocean. Those droplets can evaporate down to droplet nuclei and float away.

“Airborne diseases also took advantage of the social lives of animals. As some species evolved to live in close groups–in nests, burrows, flocks, and herds–they made it easier for a cloud of exhaled pathogens to infect a new host. It's likely that airborne diseases have fared best among animals that live together. If a solitary creature breathes out microbe-laden droplets, they may fail to reach another member of its species before they fall to the ground or get damaged by sunlight. In a herd or a den, a sick animal can release clouds of pathogens that have better odds of getting inhaled by another nearby host.

“Measles, the most infectious pathogen ever found, belongs to a family of viruses that typically infect grazing mammals. Some infect seals. While seals spend much of their lives out at sea, they also haul out onto beaches where, huddling together in groups, they mate, raise their young, and breathe viruses on one another. Dolphins get their own form of measles too. While they never come ashore, they still have lungs and breathe through blowholes–a legacy of their terrestrial ancestors, which lived on land 50 million years ago. Swimming in pods, they surface together to exhale blasts of air and suck in new ones. The measles virus takes an airborne hop before the dolphins dive underwater again.

“When aerobiology emerged in the 1930s, it generated great excitement, but within a few years it faltered. In World War II, the United States and other countries recruited aerobiologists to make biological weapons. And when the war ended, the aerobiologists kept on growing pathogens to wipe out cities and starve nations. A shroud of secrecy fell across much of aerobiology. Even today, the science is not entirely free of it.

“In those postwar years, some aerobiologists tried to persuade public health officials to take the threat of airborne infection seriously. They largely failed. Infectious disease experts who led the fight against outbreaks and prepared for the emergence of new diseases mostly ignored the aerobiologists, even when it meant accepting some basic mistakes about the physics of air.

“The Covid-19 pandemic finally rattled that consensus. In so doing, it provided an opportunity to rethink our history with the air. The Covid-19 pandemic was not a fluke. It belongs to a deep history of airborne life, one that has adapted with astonishing efficiency to our species's rapid rise–from the dawn of agriculture ten thousand years ago to the rise of cities, to the Industrial Revolution, and now to the twenty-first century's megacities and decimated wilderness. SARS-CoV-2 is only one species in an airborne habitat that we largely ignore, but would do well to understand.”