Remaining indoors with members of our household (sheltering-in-place) is the best way to prevent the spread of COVID-19 to or from persons outside our homes. But we must not forget that going outdoors has numerous well-established physical and psychological benefits while being confined indoors has substantial adverse effects, including the public health risk of epidemics caused by delayed childhood vaccination. And there is emerging evidence that our chances of contracting COVID-19 outdoors are likely lower than under similar circumstances indoors.
The benefits of being outdoors are documented in dozens of peer-reviewed scientific publications (summarized here). Greenspace activities are associated with better general and mental health, independent of urbanization, socioeconomic status, and gender. Benefits have been found for all age groups, and are especially essential for children. Time spent outdoors leads to more physical fitness and less sedentary behavior. It is well established that being outdoors can prevent or mitigate the impact of health conditions such as vitamin D deficiency, myopia, multiple sclerosis, and Alzheimer’s disease. Exercising outdoors (compared to indoors) leads to greater revitalization. There are also mental health benefits, especially stress reduction and decreases in tension, confusion, anger, and depression. People report greater enjoyment and satisfaction with their physical activities when outdoors.
The recommendation of maintaining a distance of six feet from others while outside of our homes is based on longstanding (albeit not universally accepted) evidence that transmission of respiratory viruses primarily occurs when we are in close physical proximity. COVID-19 appears much more common in indoor spaces. Although we worry about transmission over longer distances by aerosols, there seems to be only one reported COVID-19 outbreak where close physical contact could not be documented —in an indoor public bathhouse in China.
A recent study from China found no outbreaks of three or more cases originated outdoors, even before the implementation of lockdowns. A study in Japan estimated that the risk of infection indoors is almost 19 times higher than outdoors.
Distance, ventilation, and sunlight matter and most outdoor spaces offer plenty of all three. CDC recommends outdoor collection when testing for the causative virus when possible, and prioritizes outdoor seating as restaurants reopen. Medical experts have recommend. Even inside hospitals caring for known COVID-19 patients, isolation rooms that prevent aerosol transmissions are reserved primarily for people who have infections known to be airborne, such as measles and tuberculosis. Such rooms are recommended only for COVID-19 patients who are undergoing procedures known to produce aerosols. One needs only to think about persons smoking outdoors versus indoors to understand that exhaled aerosols disperse more rapidly outdoors. Such ventilation is one of the most important means to control cross infection by virus-laden exhalations. We fear that infectious virus particles from people infected with COVID-19 may contaminate surfaces outdoors as well as indoors, but, as with aerosols, no case of transmission from contact with such surfaces has yet been documented.
In a landmark article, Risk within Reason, Richard Zeckhauser, a Professor of Political Economics at Harvard University, reminded us that humans disproportionately fear improbable events. We suggest that it is likely that with the proper practice of social distancing, handwashing, and use of face coverings when we are within 6 feet, the risk of contracting COVID-19 outdoors is lower than many of us fear.
We will not be in a no-risk situation until long after a vaccine is available, which is likely to be many months away at the earliest. In the interim, we will need to learn to accept some risk, especially those that offer substantial benefits–like being outdoors. Infectious disease experts are suggesting our guidance regarding outdoor activities is too restrictive and Cleveland clinic has issued guidance on how to remain safe outdoors.
Daniel B. Fishbein, MD, is an infectious disease and public health physician retired from the Centers for Disease Control and Prevention. Ben Pettit is an attorney in Santa Barbara.