You’ve probably seen this diagram from a Chinese study somewhere already, but in case not, give it a look. Note the position of the A/C unit.

That’s the layout of a restaurant in Guangzhou, involving an actual case of COVID-19 in late January. A1 was a patient infected with the virus who had recently arrived from Wuhan. Researchers theorize that that one person infected nine other people in the dining room that day thanks to the air conditioning unit positioned across from her. The theory is that the A/C blew the virus she was expelling back across Table B and against the wall, where it rebounded and eventually traveled all the way across to Table C. No diners on the other side of the dining room (not shown here) were infected.

The moral of the story: Confined spaces are hazardous to your health during an epidemic. Which we all already knew, but about which we’re all in some degree of denial due to our yearning to get back to normal.

But there’s a silver lining. Maybe we can safely resume many of the activities we miss if we eliminate the “confined space” part of the equation. A new study from China that looked at hundreds of local outbreaks (not including Wuhan, notably) found that transmission of the virus outdoors was all but unheard of.

Case reports were extracted from the local Municipal Health Commissions of 320 prefectural cities (municipalities) in China, not including Hubei province, between 4 January and 11 February 2020. We identified all outbreaks involving three or more cases and reviewed the major characteristics of the enclosed spaces in which the outbreaks were reported and associated indoor environmental issues. Results: Three hundred and eighteen outbreaks with three or more cases were identified, involving 1245 confirmed cases in 120 prefectural cities. We divided the venues in which the outbreaks occurred into six categories: homes, transport, food, entertainment, shopping, and miscellaneous. Among the identified outbreaks, 53.8% involved three cases, 26.4% involved four cases, and only 1.6% involved ten or more cases. Home outbreaks were the dominant category (254 of 318 outbreaks; 79.9%), followed by transport (108; 34.0%; note that many outbreaks involved more than one venue category). Most home outbreaks involved three to five cases. We identified only a single outbreak in an outdoor environment, which involved two cases. Conclusions: All identified outbreaks of three or more cases occurred in an indoor environment, which confirms that sharing indoor space is a major SARS-CoV-2 infection risk.

Here’s what it looks like on a graph, with outdoor cases so few that they don’t even show up. Restaurants are relatively low-risk but obviously not no-risk.

If you’re wondering how the hell New York City can still be seeing new cases five weeks after everyone locked down, there you have it. A lot of it is likely happening at home, as one infected family member eventually infects another family member, then they eventually infect another, and so on. (An example of this played out on CNN, when Chris Cuomo got sick weeks ago and his wife came down with the disease weeks later.) The high risk of spread within families is why lots of experts favor setting up centralized quarantine facilities. If we sent sick people to some sort of dormitory for two weeks to convalesce instead of sending them home to infect their families, we could minimize outbreaks.

But I digress. The takeaway here is that the more business and entertainment we can move outdoors, the safer it’ll be to reopen. Restaurants could shift to al fresco dining. Religious services and fitness programs could be done in the open air. Even certain retail businesses might try to hawk their goods with display tables set up outside. If you like what you see, the sales clerk could fetch the product for you from inside the store. I see lots of tents set up in parking lots in our collective future. (Don’t ask me where people will actually park their cars.) Open-air retail plus ubiquitous mask-wearing plus basic prudence in social distancing, e.g., six feet of room between everyone, could make many business activities more or less safe.

Uh, could meatpacking be done safely outside? I’m thinking “no way” due to the risk of bacterial contamination but I’d welcome a correction, as we’re staring at a potential meat shortage due to the virus spreading like wildfire through multiple meat processing factories.

One thought that occurred to me while reading the abstract of the Chinese study was “What about that mid-February soccer match in Italy?” That was played outdoors, of course, yet researchers believe it contributed enormously to the ruinous spread of COVID-19 in Lombardy. But then I remembered this part:

Atalanta supporter Luca Brignoli, 57, thinks back to his subway ride to the San Siro from downtown Milan, bodies jammed against the door. He remembers milling around the piazza in front of the stadium, where fans from both sides mixed and drank and snacked from food trucks. He wonders how many people might have coughed or sneezed while navigating the stadium’s turnstiles and narrow passages.

“People went as if to a feast,” said Mr. Brignoli, who hasn’t displayed any symptoms. “We were very close to each other.”

Being outdoors may minimize the risk of infection generally but less so if you’re packed in like sardines. That infamous parade in Philly in 1918 was also held outdoors, of course, and you know what happened there. Density is surely a factor even in outdoor spaces. And mass sporting events usually involve activities before or after the game, like tailgating, where people are sharing food and drink — sometimes indoors, like the bars outside stadiums. Even if the feds adopt a “Do as much as you can outdoors” policy, they’re not going to say it’s okay to go to baseball games anytime soon.

The institutions that should start thinking the hardest about functioning outdoors are schools. It wouldn’t be easy. They’d need to find sufficient space for multiple classes to meet at the same time, while observing social distancing. They’d need to plan for bad weather. They’d need to somehow keep children, especially small children, focused on the lesson instead of on wanting to run around and play. But I don’t know what the alternative is to outdoor classes if we don’t want kids missing even more education than they already have. One idea would be to reopen schools soon and teach right through the summer, weather permitting, in the belief that schools will have no choice but to close again this fall as the second wave of COVID unspools. Kids can’t be taught outdoors during winter; if you want to squeeze in some knowledge before it’s infeasible to gather them outside again, summer’s the time to do it.