COVID19 Exposure Risk: Exposure risk to coronavirus is not an all or nothing proposition. Risk is relative. Some types of interactions carry some risk, others carry much higher risk. Some considerations are as follows.
- Brief vs Prolonged – Spending 10 minutes speaking with someone is very different from engaging in a 2 hour conversation. Even with 6ft of separation, prolonged interactions increase the risk of transmission. While larger droplets typically do not travel farther than 6ft, smaller aerosolized droplets can. And the longer you are interacting with another person, the more exposure you will have to each other. Masks are recommended to help reduce the risk of transmission during prolonged interactions (even at distances greater than 6ft) such as in workplaces or other situations where longer conversations are expected. More reading on this topic can be found here.
- Small vs Large Groups – A gathering of 3 people is different from a gathering of 10 people, which is different from a gathering of 50 people. The more people, the more challenging it is to maintain adequate physical distancing and the greater the likelihood of coming in contact with someone who might be infected. More people also means there is an exponentially higher risk of spread to other groups. Masks are recommended to reduce transmission risk and should ideally be worn throughout gatherings of more than 3 people. It is impossible to wear a mask while eating and drinking, and meals are often longer than 15 minutes. Therefore, meal gatherings with people from more than one household are strongly discouraged.
- Normal vs. Loud Speech – Droplets from your respiratory tract are unlikely to travel farther than 6 ft during normal speech. But when you are speaking loudly or singing, your respiratory droplets may spread much farther. Masks can help to reduce this spread. Note, that most masks will not contain droplet spread entirely. The effectiveness of the mask and the fit of the mask will play a large role in this matter. Facial hair, for example, can reduce the seal of a mask. Also, most home-made masks will not filter out most respiratory droplets and virus particles. This said, a properly worn mask of any kind is better than no mask. But note that unless you are wearing a fit-tested (tested in a health professional setting) N95 mask, you are still spreading droplets when you are speaking loudly with a mask on, so more distance is recommended.
- One-time vs Frequent – A single brief gathering with a small group of individuals may be only a modest risk. However, if that group gathers multiple times per day, every day, every week, the risk multiplies and quickly becomes very significant. This is one reason that a minyan (which a person will attend 14-21 times per week) is considered much higher risk than supermarket shopping (which is typically done only once or twice a week).
- Isolated vs Mixed Groups – When individuals from separate groups interact, they effectively link their groups into a single larger group where transmission can occur. Over time, people who are infected with COVID-19 will continue to bring the illness into the community from outside sources. Even small amounts of intermingling greatly increases the chance of widespread transmission. If we restrict our contact to the same people and do this in the safest way possible with masks and distancing, it will greatly reduce the likelihood of an explosive outbreak if one person gets sick. However, if individuals from within a group are mixing with other groups regularly, the chance of COVID19 spreading widely throughout the community is very high. This is especially true when isolation bubbles grow too quickly and or when members of isolation bubbles are not practicing proper physical distancing with their friends and acquaintances outside of their homes.
- Outdoor vs. Indoor – Virus particles are able to spread farther and linger longer in closed spaces. In addition, distancing is often more difficult indoors. Active ventilation of indoor spaces may decrease risk, but outdoor interactions have a lower overall risk of spread. This is not to say that COVID19 transmission does not occur during outdoor gatherings. In fact, an outdoor soccer match is thought to have been a significant factor in Europe’s COVID19 outbreak (reference). This said, outdoor venues appear to be safer and preferred over indoor spaces.