In the Western world, humans spend 90% of their time indoors. The average American spends even more than that—93%—inside buildings or cars. For years scientists have sounded the alarm that our disconnect from the outdoors is linked to a host of chronic health problems, including allergies, asthma, depression, irritable bowel syndrome, and obesity. More recently, experts in various fields have begun studying why buildings, even those designed to be as germ-free as possible, are vectors for disease, not the least Covid-19.
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Leung says a “misalignment with nature” in building design is partly to blame for our scourge of chronic diseases and the current pandemic. The relative lack of air flow and sunlight is an obvious issue; temperature, humidity, and indoor air pollution also play a role. But there’s another, less discussed factor: the microbiome of the built environment, which encompasses trillions of microbes including bacteria, fungi, and viruses.