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The chart above is from the website Rt Covid-19 created by Instagram co-founder Kevin Systrom. The website purports to be tracking the effective reproduction number of the virus that causes COVID-19 by localities:
Most people are more familiar with R0. R0 is the basic reproduction number of an epidemic. It’s defined as the number of secondary infections produced by a single infection. If R0 is greater than one, the epidemic spreads quickly **. If R0 is less than one, the epidemic spreads, but limps along and disappears before everyone becomes infected. The flu has an R0 between one and two while measles sits in the high teens. While R0 is a useful measure, it is flawed in an important way: it’s static.
We’ve all witnessed that humans are adaptable. Our behavior changes, whether mandated or self-prescribed, and that changes the effective R value at any point in time. As we socially distance and isolate, R plummets. Because the value changes so rapidly, Epidemiologists have argued that the only true way to combat COVID19 is to understand and manage by Rt.
I agree, and I’d go further: we not only need to know Rt, we need to know local Rt. New York’s epidemic is vastly different than California’s and using a single number to describe them both is not useful. Knowing the local Rt allows us to manage the pandemic effectively.
States have had a variety of lockdown strategies, but there’s very little understanding of which have worked and which need to go further. Some states like California have been locked down for weeks, while others like Iowa and Nebraska continue to balk at taking action as cases rise. Being able to compare local Rts between different areas and/or watch how Rt changes in one place can help us measure how effective local policies are at slowing the spread of the virus.
Tracking Rt also lets us know when we might loosen restrictions. Any suggestion that we loosen restrictions when Rt > 1.0 is an explicit decision to let the virus proliferate. At the same time, if we are able to reduce Rt to below 1.0, and we can reduce the number of cases overall, the virus becomes manageable. Life can begin to return to ‘normal.’ But without knowing Rt we are simply flying blind.
“[I]f we are able to reduce Rt to below 1.0, and we can reduce the number of cases overall, the virus becomes manageable. Life can begin to return to ‘normal.’ ” The chart above suggests we are in a good place. Particularly when you see it has part of a trend line. The following graphs show the progress using the same calculation methodology from 4 weeks ago, to last week:
They last tweaked their model on 4/26 but re-ran the updated model against their complete dataset, so they are comparing “apples to apples.” Their model may be good or not, but it does seem to confirm observational data: the epidemic has definitely slowed in this country.
But do people really see that? Yes, a lot of people are anxious to get back to life. But are they feeling confident that doing so is the right decision? How do you persuade those that remain fearful that the “quarantine breakers” are actually common-sense individuals not just recklessly selfish?
This is going to be tough. The public has been fed a lot of data where the numbers rise steeply. As the body count mounts, and it will continue to do so, how do you get people to realize that things are winding down? Observational data is always the most powerful: “Who are you going to believe? Me, or your lying eyes?” the old joke goes.
The President has shifted his focus away from the health crisis to how we get our economy back. That is a start. The people going to the beach and surrounding their capitols and city halls also contribute to the pressure to get back to work. But media and the progressives are highly invested in the narrative of fear. They will continue to amplify “confirmed cases” and obscure the fact that the rising case count is actually good news so long as the rate of serious illness and death continues to fall. Testing confirms the prevalence but not the severity of this illness.
Keep an eye on hospitalizations in your area. If hospitalizations continue to fall, it is really over. Ask your social and church groups when they think it will be ok to meet in real life? Prompt their questions about how to interpret what their eyes are seeing.
One by one, we emerge into the light.
[Note: Links to all my COVID-19 posts can be found here.]Published in