Close your eyes and picture it. A solitary figure, twirling joyfully, surrounded by mountains, trees, and edelweiss. Social distancing at its best. The hills may be alive, but they’re not crawling with COVID-19. We know there’s virtually no chance of encountering the virus when you are outdoors and alone.
But pristine alpine meadows are not part of everyday life for most of us, and we face complex risk-assessment challenges on a daily basis: Is it safe to rent a car? Stand downwind of another person? Fly in a plane? Attend a protest?
We’ve answered these questions and many more recently. But you don’t always have time to send a question to CovidQ@mit.edu, never mind wait for an answer. The pandemic continues, even as previously shuttered businesses reopen, people return to work, and a new school year begins. How do you assess the risk of a novel situation or activity? What should you do when you need to make a safety judgment on the fly?
We’re here to help.
Let’s start with the Japanese government’s very effective COVID-19 messaging, which advises people to avoid the “three C’s” — closed spaces with poor ventilation, crowded places with many people nearby, and close-contact settings, such as close-range conversation. In particular, they warn against clusters that combine more than one “C” — for example, a close-range conversation in a small, indoor space.
To those three C’s we would add an important fourth — continuous exposure. Your risk of contracting COVID-19 in a closed space, crowded place, or close-contact setting increases steadily as long as you remain in that situation. In other words, 60 seconds in a crowded, indoor space is relatively low risk; 20 minutes in that same situation raises the risk level to “yikes.”
These factors can be used to assess the risk for many activities and situations. For example, ask yourself:
Where will I be? Outdoor settings are safest, but if you’re going to be indoors, how large is the space, and how good is the airflow? Can it be improved by opening windows or doors? Scientists continue to debate how the virus spreads through the air, but there’s no question that outdoors is safer than indoors and that ventilation matters.
How many people will be there, and how close will I be to others? Numbers are important, but absolute density is the most crucial factor. One hundred people physically distancing in a large park presents far less risk than 25 people mingling in a small backyard.
What will I be doing? What will other people be doing? Because the virus spreads through respiratory secretions, activities that release more respiratory droplets — like talking, singing, or shouting — increase risk.
Will I be with people who are equally committed to taking precautions and staying safe? Masks and physical distancing go a long way toward mitigating risks. But while your mask may protect you to some extent, if others are unmasked and not making an effort to maintain a safe distance, the risk level increases significantly.
And with Labor Day weekend upon us, it’s worth noting that risks are exacerbated at events involving food and drink. While there is no evidence that COVID-19 can be transmitted through food, masks come off when people eat or drink. Alcohol consumption doesn’t help either, as people who are drinking tend to stand closer and talk louder, both of which increase the risk of transmission.
Finally, while you can use these general guidelines to assess the relative risk of any situation or activity, you should also consider circumstances that are unique to you as an individual and to the area in which you live:
Community spread is a factor that will change over time, but it’s one you should consider when making risk assessments in the moment. The Testing Trends Tool from Johns Hopkins School of Medicine can help you keep up with the numbers in your area. The “percent positive” statistic indicates how widely infection is spreading in a given area and how well testing is keeping up with levels of disease transmission. A high percent positive indicates high levels of community spread and suggests that there are many infected people in the community who haven’t yet been tested. This makes any activity that puts you in contact with people outside of your household or “bubble” much riskier.
If it all seems a bit overwhelming, we get it. It’s a lot to think about. A year ago, we wouldn’t have thought twice about attending that holiday BBQ. Now we’re being asked to weigh multiple factors that increase or mitigate risk, mentally adding, subtracting, and multiplying to calculate an estimate of the overall safety level. Planning the simplest activity requires a level of effort our pre-pandemic selves never could have imagined. It may be one of the hardest parts of daily life right now. But it can be done.
And as difficult as it may be to imagine now, there will again come a day when you’ll be able to make spur-of-the-moment plans to get together with a group of friends wherever you’d all like to go. By mindfully choosing to reduce transmission risks now, we can all play a part in keeping ourselves and our communities safe until that time.