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In Massachusetts we are proceeding to “open up” the economy step by step with detailed and carefully crafted instructions that are mostly sensible when first issued by Governor Baker through the Department of Public Health (DPH).

We can take heart that the incidence of new infections with SARS-CoV-2 is way down as is the community prevalence of active Covid-19 infections. So our overall risk of encountering an infected person is dramatically lower than just a month or two ago.

In this progressively safer environment, how should we continue our self-care and physical protection since we now can have someplace to go to other than the supermarket? We can rationally venture out of quarantine and beyond our circles of safety, with appropriate protections. In brief, we still need to be careful, but we don’t need to be crazed.

I will try to provide a simple recap that reflects what we have learned about the Covid-19 behavior in the past 3 months and clarifies how this should reflect in our self-care.

Where do infectious risks arise from Covid-19?

The SARS-CoV-2 virus is predominantly spread by person-to-person contact, mostly by respiratory droplets that travel only short distances (up to about six feet), but to a lesser degree appears also to spread by respiratory aerosols (especially from singing and shouting) that can linger in still air (read indoor) for an extended period of time (minutes to even an hour or two).

The portal of entry for the virus is almost always the nose or mouth, leading to our respiratory tracts where the virus thrives, and also by contact with the eyes, by which the virus can gain entry to the respiratory tract through the tear duct drainage. By contrast, the skin appears to be impervious to the virus as a portal of entry. The primary reason to studiously wash your hands (beyond general cleanliness) is to prevent self-infection when you unknowingly touch your face, as most people do frequently, with SARS-CoV-2 contaminated fingers.

In addition, while the majority of people with Covid-19 infections are observably symptomatic with fever and cough and muscle pains and other ailments, we have also learned that some people can be asymptomatic carriers of the SARS-CoV-2 virus and infectious to other people at the same time as they feel and appear healthy. This number is small, but real. Asymptomatic carriers must be seriously considered in the self-protection plan for most anyone in populous areas where the epidemic is active, such as eastern Massachusetts.

Finally, intensity and duration of exposure directly affect risk of infection. A certain viral load of active virus particles has to contact you and gain access to your respiratory tract. Intensity goes up if you encounter more infected people (knowingly or not), are closer to them than six feet, are in closed spaces where the air exchange is inherently slow, have no face mask or covering or an ineffective one, and are in those adverse conditions for more than a few minutes (“lingering”).

Self-defense against SARS-CoV-2 virus

Our defenses against the Covid-19 infection reflect the four determinants of risk I outlined above.

Proximity and location awareness

Keeping “social” distancing of at least six feet provide excellent against droplet spread (though perhaps not so good against aerosols), the virus’s biggest weapon.

Outdoors is really safe. It is easy to keep apart, there is usually at least a slight breeze, and droplet spread is hard to achieve. Aerosols cannot linger in the outdoors, the way they can in a smaller room. Some recent reports from China investigating the location of initial exposure found essentially no outdoor occurrences in 70,000 investigations. Masks are required outdoors at the moment, but really only for the times when people unexpectedly come close together. Outdoors is a low risk environment. Go for a walk or ride or other exercise. Don’t waste the summer.

By contrast, indoor environments with groups are inherently not low risk. This includes homes as well as small and large stores. The essence of the “opening up” process has been to define and implement physical and procedural changes at all public environments (small and large stores, office buildings, small offices, houses of worship) to lower the risk of congregating together. Methods include sharply limiting the density of people simultaneously in the facility, improving ventilation and sanitation, checking customers’ well-being before entry, and requiring PPE (personal protective equipment) for staff and masks for customers. The DPH procedures seem thorough and careful; we will all soon find out if they are effective.

Masks, masks, masks

Michigan barber’s mask under nose, client no mask [NY Times photo]

Because the nose and mouth (and less the eyes) are the primary portal of entry for SARS-CoV-2, covering those parts with some form of mask is an essential component for self-protection, especially because not everyone wears a mask nor wears it properly. But we need to match the efficacy of the mask to the risk of the environment we will be in (remember intensity and duration of exposure).

Simple cloth face coverings and surgical masks actually provide asymmetric protection. They do a good job of preventing your respiratory secretions from infecting your immediate neighbor but are much less effective in in preventing you from inhaling airborne viral particles because of the typically loose fit over the cheeks or insufficient filtering capability or both. And if the mask is worn below the nose (which I see frequently), then it is of almost no use to the wearer or adjacent people.

So the cloth face coverings and available surgical style masks should be fine for you to use (when coupled with social distancing) where the intensity and duration of SARS-CoV-2 exposure are low, such as for brief forays into indoor environments (supermarkets, clothes shopping in a store with restricted customer entry for short periods), or moderate duration visiting with another couple at their home in a large room or on a porch, and so forth where distancing can be maintained, and of course if needed outdoors. In addition, available cloth and surgical masks likely also will prove adequate for prolonged use in commercial offices that have sharply reduced the worker density according to DPH guidelines.

However, in my risk/benefit evaluations, cloth and surgical style masks do not really provide sufficient protection to the wearer in higher risk situations, such as prolonged indoor stays with groups, where the risk of spread from an asymptomatic carrier or presymptomatic infected member will be highest. How to allow people to gather in theaters or houses of worship with an attainable level of self-protection consistent with this higher risk remains the largest issue in “reopening.” I am not certain we have the right practical answer yet to these indoor group gatherings.

For clear high risk (exposure intensity and duration) settings, only properly fitted N95 respirator masks (at least 95% of small particles are blocked) are likely sufficient for realistic protection from people with active Covid-19 infections. High-risk settings, for example, would include packed audiences in pre-Covid-19-style theater presentations or church holiday services, in addition to hospital emergency rooms. But N95 masks need to fit properly (snugly with good seal) otherwise they are not effective, they are harder to breathe in especially for any extended time, and are still really hard to come by, even for professionals. Even then, in many high-risk settings face shields are appropriately recommended in addition to N95 masks and certainly for surgical masks. We struggled to amass enough PPE for us to open our offices safely (which we will shortly do, as described in another post).

General sanitizing procedures

Keeping our hands clean is critical to self-protection from Covid-19. It is hard to overemphasize this reality.

We must continue to wash our hands (and faces) frequently and thoroughly with soap and water (20 seconds or two Happy Birthday recitations), and especially after any apparent environmental exposure, or use hand sanitizer when a sink is not available.

SARS-CoV-2 survives poorly on dry and porous surfaces, likely not more than 24-48 hours on boxes or mail that conceivably was handled by an infected delivery person. It can last perhaps 3 days on metal or plastic surfaces. At home, Amazon boxes and mail are really low risk. Think of the unlikely chain of events that would have to happen to have a sizeable inoculum of live SARS-CoV-2 on a box or the mail when you get it.

You can open boxes and mail without touching the insides, wash your hands, and then finish unpacking. Or you can let the boxes and mail sit for 48 hours and then open them with essentially no risk of contaminating the insides, but still wash your hands afterwards. Gloves are not really an improvement because the glove outsides are theoretically contaminated just as your hands might be, and you have to take them off, which is difficult to do without again getting your hands contaminated.

In other words, treat every incoming box at home the way you treat chicken. You don’t wash the chicken (which spreads the salmonella all over your kitchen), but you wash your hands carefully afterward (and with chicken you also wash before!).

Finally, you should sanitize your kitchen counters once a day, which is appropriate to protect against e. coli and salmonella food contamination, not just SARS-CoV-2. Use an EPA certified sanitizer (list available on EPA website). For simplicity most any Clorox kitchen sanitizer will be on the list.

In summary (I was compact, but not brief)

Summer is here. The SARS-CoV-2 virus is a much lower but still present risk. It is not going away completely any time soon. Keep in mind the issues of exposure intensity and duration when you plan your activities. Use appropriate PPE. Providing we are prudent and follow these appropriate self-protective measures, which I just reviewed, we can safely venture out of quarantine and beyond our circles of safety. Be prudent but not afraid or crazed.

In another post I will detail how we have prepared to reopen our Orchard Health Care office for urgent care.


  • Howard Bloom says:

    Good evening — would like to read your opinion and suggestions about allowing third parties, such as plumbers, cleaning help, in our homes. Thanks.

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