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I’m out of my Atlanta supermarket, counting. And they have been every day since March 29. How many people are buying alone? A lot (86%), and I would like to know what the proportion was two months ago to measure a possible change in this form of social distancing. How many wear masks? A lot. And this time I knew the ratio two weeks ago. In the three days after a March 28 national paper editorial advocating the informal use of masks, he averaged 13%. A week later, perhaps helped by the CDC’s recommendation to voluntarily wear informal masks if social distancing measures were not practical, the proportion quintupled to 69%. Here’s a graph (for statistically minded people, r2= 71.9%, P= 0.0002):
Older people did as well as younger ones. Perhaps surprisingly, given the recent emphasis on apparent disproportionate cost in black America, blacks were more likely than whites to wear masks (P<0.05). Some people will never wear masks. We should know why. Because then we could achieve 100% use. If that is what we want to do.
But understanding what we want to do implies knowing the value of “what”. And the value of our public health recommendations that lead to the “what”. So I am writing.
When the SARS-CoV-2 epidemic subsides, we must know why. In times of emergency, we rightly throw a basket of interventions at a problem in the hope that something will work. In this case, social distancing (consisting of a variety of interventions and not just standing 6 feet apart from each other; the CDC lists “staying out of congregated settings, avoiding mass gatherings, and keeping distance from others. [approximately six feet] whenever possible “), intensive hand washing, avoiding contact with the face, surface disinfection, aerosol decontamination, masks, tests, contact tracing, etc.
At its extreme, social distancing may imply the closure of companies and schools. Some interventions will be more effective than others. Some could backfire if people practice them instead of more effective measures. Going home from the store, throwing our clothes in the washing machine, and showering will be good for soap makers, but not to stop the spread of the coronavirus. We must know what has been effective and how effective. Then we can prioritize the most useful interventions and eliminate the bad ones.
What if the use of masks were 70% as effective in preventing cases as social distancing? We may not close businesses or schools, but we want 100% of people to wear masks and do so appropriately. And how effective was closing the economy against other measures? What if contact tracking, which is now increasing, adds another 20% to mask usage so that mask usage and contact tracking achieve 90% of what the economy closed? Wearing masks and tracing contracts may even be more effective than social distancing.
And which of the multiple parts of social distancing was more effective than others? In a nongenerable online survey of 6,689 Americans conducted between March 14 and 16, while adopting a group of social distancing measures, each with different efficacy (97.7%), the increase in handwashing was the most common lifestyle change made in response to COVID -19 (93.1% of the respondents). That was an interesting finding since 74.8% in another online survey conducted from February 23 to March 2 that involved 2,986 Americans thought (probably correctly) that airborne drops from a close person were the most likely way to infection.
We need to know the magnitude of the modes of possible transmission of the virus and which of our prevention recommendations (and subsequent adoption by the public) most effectively stop this transmission. If Americans stay 6 feet away, or stay home, or wear masks, or give up the handshake, or whatever, we need to know how effective each is at preventing CoV-2 infection from SARS, and compared to other measures. We can learn from our own national, state or even local efforts, and from the efforts of other countries.
Difficult questions but for which we must get answers. While something works to reduce infection rates, we don’t fully know what. The time to start collecting this information was yesterday. We must know when the recommendations were made and to what extent the public practiced them. Otherwise, finding associations between infection rates and adoption of interventions becomes difficult; Memories of what we did yesterday are inaccurate. Epidemiological and microbiological studies can address the determination of the effectiveness of interventions.
Hopefully, my former colleagues at CDC and the World Health Organization have been making those efforts and will have answers, even if they are imperfect. If not, we will be repeating the unpleasant basket of interventions if a second wave of SARS-CoV-2 arrives, if things don’t go well after states open, or if another virus appears in the coming years. Tens of millions of Americans have lost jobs due to SARS-CoV-2. The public will not be eager to repeat the entire basket again.
George Schmid, MD, is an infectious disease physician and epidemiologist, retired after 38 years with the CDC and the WHO.
