Social Distancing

I want to begin by saying that social distancing is important and effective and I support its use to limit the spread of this coronavirus. Right now, this is really our only tool to combat COVID-19. Hopefully we will have approved chemotherapeutics and a vaccine sometime this summer. One must realize, though, that social distancing covers a broad spectrum of conditions. Too many people are approaching this as a binary situation - ON vs OFF. Moreover, our state leaders are treating the entire state monolithically (assuming that the risk of COVID infection and/or death is uniformly distributed across the state). The Governor’s orders are applied equally to all counties and precincts regardless of the disease incidence in those locales (we are all completely shut down except for ‘essential’ services). In addition, several of the most recent orders seem to have more to do with controlling business than disease. To wit: limiting which items can be sold at a store like Menards. This makes no sense from an epidemiological point of view. Once you are at the store, you have experienced the same risk of contracting COVID whether you buy plumbing supplies (essential) or a tomato plant (non-essential). These political decisions are worrisome for several reasons. First, shuttering small businesses is causing measurable economic harm. If there is not a sufficient upside (preventing measurable disease) these measures are not justified. Second, if we go from all OFF (stay at home) to all ON (everyone back to your normal lives), there is a risk of a second re-emergent spike of infections. What we need is a rational and graduated approach to social distancing and social restrictions. Here is my proposed approach.

Current Reporting and Room for Improvement

The state of Michigan already collects overall incidence data for COVID-19 by county (that is as granular as we probably need to get for responses in any case). One such graph is shown to the right. As one can readily see, cases are not uniformly distributed, but rather concentrate in the Detroit metropolitan region. Also, these are overall incidence numbers (since the beginning of the outbreak in Michigan). We need to see period incidences instead (the number of cases occurring in a specified time period). I suggest cases reported over the past two weeks - since that ought to account for the infectious period of this disease. I then think that our social restrictions should be made - county-by-county - according to the risk of infection (period incidence) in those locations. To make it easier for the public to comprehend, a color coding system could be implemented.

Color-Coded Risk Categories

In a manner similar to the terrorism risk system, I would suggest a four-tiered color system to categorize and respond to COVID-19 threat levels. While I think that these levels should be based upon the period incidence, I do not have specific thresholds in mind. Trained epidemiologists would be able to provide better numbers than me. I will suggest a few for discussion purposes. But I would defer to those with more expertise when the time to create real thresholds arises.

RED - This represents the most severe outbreaks (100 or more cases reported in a 14-day period) and should have correspondingly tight social restrictions. Stay at home should be mandatory for all non-essential workers. Travel to and from red counties should be curtailed as much as practical. All non-essential businesses (groceries and fuel - yes, hardware and personal care - no) should be closed. Group meetings outside of immediate family members should also be limited. In adddition, the state ought to be redirecting medical personnel and supplies from green and yellow counties to the red and orange ones to fight where the battle is the hottest.

ORANGE - This level corresponds to a moderate level of risk (between 10 and 99 cases reported in a 14-day period) and should have somewhat fewer restrictions. Travel and business restrictions should be loosened a bit. Hardware stores and others should be allowed to operate with limited hours and limitations on the number of people on premises at any one time. With proper social distancing, some small groups (perhaps less than ten) should also be allowed.

YELLOW - This is a low risk of disease; I envision this as something between 1 and 9 cases reported over a two-week interval. At this level, there should be a few restrictions in place to safeguard against an exponential breakout. All small businesses should be allowed to operate and groups of 20 people or less could be allowed. However, a six-foot spacing rule should be enforced to reduce the likelihood of easy person-to-person spread. Most counties in Michigan would be yellow at this point in time. This status would allow many people to return to work (as plumbers, roofers, hairdressers, etc.) while adding very little threat of precipitating a COVID crisis.

GREEN - This is the ‘all clear’ state. Green counties would have no reported incidences of COVID-19 in the past 14 days. As such, people should be free to go back to work and interact normally. Groups meetings of 100 or less should be allowed, since the probability of infection is low and near to zero. If a county is green for a longer period of time (something like four consecutive weeks) somewhat larger groups could be allowed - on the order of 1,000 people. Once the entire state is green, even larger group events could be allowed again.

Advantages

A tiered, color-coded COVID threat system like this has several advantages. This scheme is objectively based on measured threat levels and clearly articulated. People would have little trouble figuring this out and it is easily shown on summary maps. This system is also adaptive. If a yellow county experiences a spike in cases, it will become orange and more stringent controls will automatically be enacted. Likewise, if an orange county reduces its incidence to become yellow, then its restrictions will be eased accordingly. People will want their county to become green and will avidly track these weekly map statuses. My guess is that yellow counties will go over and above the necessary restrictions just to make it to green without further government coersion or oversight. The goal, of course, is to reach the point when the entire state is green. In all likelihood, that will be sometime in June or July. It seems to me that this (or something like it) is the only rational exit strategy for our COVID interventions. We must be willing to accept some small risks in order to safely return to a somewhat normal life. Well, those are my thoughts on the matter. What do you think?