The outdoors, exercise, sunshine, and fresh air are all good for people’s immune systems and health, and not so great for viruses. There is a compelling link between exercise and a strong immune system. A lack of vitamin D, which our bodies synthesize when our skin is exposed to the sun, has long been associated with increased susceptibility to respiratory diseases. The outdoors and sunshine are such strong factors in fighting viral infections that a 2009 study of the extraordinary success of outdoor hospitals during the 1918 influenza epidemic suggested that during the next pandemic (I guess this one!) we should encourage “the public to spend as much time outdoors as possible,” as a public-health measure.

Mental health is also a crucial part of the resilience we need to fight this pandemic. Keeping people’s spirits up in the long haul will be important, and exercise and the outdoors are among the strongest antidepressants and mental-health boosters we know of, often equaling or surpassing drugs and/or therapy in clinical trials. Stress has long been known to be a significant suppressor of immunity, and not being able to get some fresh air and enjoy a small change of scenery will surely add to people’s stress. We may well be facing a spike in suicides and violence as individuals and families face significant stress and isolation: The Air Force Academy initially imposed drastic isolation on its cadets due to the coronavirus, but had to reverse course after two tragic suicides. Domestic violence is another real concern: Not having a place to go, even for an hour, may greatly worsen conditions in some households.