Not a Peak, more of a Ridge Walk

By: Foss Tighe
May 2, 2020

The first blog post on this site talked about what the other side of the curve might look like. It speculated that the other side of the curve would look nothing like the first side of the curve. Most of the models being used, including IHME at the University of Washington, which has been cited by the US Coronavirus task force, were predicting a more or less symmetrical curve. However, the data in US overall, and Massachusetts where I live, has not shown a distinct peak followed by a sharp decline. Instead we seem to be hiking along a high ridge, with an occasional false summit. Figure 1 shows daily new detected cases in the United States. On April 7th, the US hit 30,000 newly detected cases, since that date we have continued to hover around 30,000 new cases each day. Figure 2 shows a similar pattern for daily deaths. Having first broken the 2000 per day point on April 7th, the daily body count has continued to hover around 2000 per day.

Figure 1: Newly Detected Coronavirus cases in the United States – Showing new cases hovering around 30,000 per day since April 7th
Figure 2: Daily Deaths in the United States. On April 7th daily deaths first went above 2000 per day and have continued to average around 2000 per day since then. (https://www.worldometers.info/coronavirus/country/us/)

Some countries in Europe show a downward trend after a peak, but these downward slopes are not nearly as steep as the rise to the peak. Figure 3 shows deaths in Italy. They went from 0 to their peak in under a month, while 5 weeks after the peak we are still seeing 250 deaths per day.

Figure 3: Daily deaths in Italy went from 0 per day in late February to a peak on 3/27. Five weeks after the peak there are still 250 deaths per day.

The lack of a symmetrical curve should have been no surprise. The bell shaped curve associated with an infectious disease outbreak is symmetrical because once enough people have been infected with the disease it gets harder for the disease to find new susceptible people to infect. This is referred to as herd immunity. With herd immunity the number of new infections declines rapidly eventually reaching zero. However, we did not allow the infection to run its natural course, instead most countries instituted various forms of social distancing, to “flatten the curve”. The goal was to reduce the speed of the outbreak, so that at no one time would the health care system be overwhelmed by the number of people needing care. The problem was that the social distancing needed to flatten the curve and protect the health care system, was so great, that we have not come near to the level of population infection needed to start a natural and rapid decline in infections and deaths.

So the course of infection is now being driven mostly by social distancing. Recent anti-body data from New York indicates that perhaps 21% of people in New York City may have already had the virus. With such a highly infectious virus as Coronavirus, this is not a sufficient level to cause a decline in new infections on its own, but in conjunction social distancing it will reduce new infections.

So in places with aggressive social distancing, we will see downward slopes like in Italy. New York State is also in a gradual downward slope, though like Italy, hundreds of people are still dying each day. In Massachusetts it seems that the level of social distancing has struck a balance where new cases and deaths are neither increasing or decreasing. Figure 4 shows the Massachusetts daily detected Coronavirus data. On April 9th the daily total first rose above 2,000. Since than there has been fluctuations but the daily totals have continued to hover around 2,000 per day.

Figure 4; Massachusetts daily detected Coronavirus cases.

Too Much Focus on the Surge:

The fear that we would exceed the capacity of our health care system resulted an almost exclusive focus on the “Surge” and the need to “Flatten the curve”. This has led to a situation where there was almost no focus on what would happen after the “Surge”. There was an almost mythical belief in the bell curve. Once our valiant social distancing had allowed us to survive the “Surge”, the virus would somehow miraculously disappear.

But instead of bagging a peak, we find ourselves on a ridge walk.

We Need A Plan:

Flattening the Curve is only a plan for the initial outbreak, it is not a plan that gets us through the 12 – 18 months needed to develop a vaccine. State and Federal authorities need to develop plans for this ridge walking period. Such plans need to be coherent and believable, as pretty much all possible plans will require the active participation of the citizenry for them to succeed.

The most talked about plan is a return to a containment strategy bases on effective case detection, contact tracing and isolation. But there are others based on trying to navigate a path to herd immunity while somehow providing extra protection for the elderly and those with underlying conditions. The lack of a clear “post surge” strategy is leading to a dangerous break down in the social fabric in the United States. As we are increasingly seeing a partisan divide based on the need to “Fight the Virus” vs “Open up the Economy”.



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