12. Weekly Update: All Populations are in Recovery

(4/22/20) The world continues to recover with all hot-bed countries showing declining death rates. The U.S. has turned the corner, but appears about 2 weeks behind the rest of the world, with the U.K. being the other laggard. Our estimates for when gradual easing of social restrictions has pushed out a few days since last weeks forecast.

Remember to check my post called “Daily Rumblings” for late breaking updates.

We’ll continue our routine of presenting the death rates internationally and domestically and from that and other conditions and assumptions detailed in our Model from previous postings we forecast total deaths, prevalence and incidence of cases and easing dates. We also compare our forecasts with that of the heralded UW IHME model.

Before we go on, please see the previous posting (just posted): “11. Recommended Guidelines for Easing of Social Distancing.”

The plots below show the familiar death rate curves for hot-bed countries (we may drop S. Korea and China in the future) and for U.S. states. We have upgraded the severity scale (3-color ranking) for some of these. The U.S. remains the only country still ranked as serious with a red spot. Several states are still in that category as well.

The qualitative red, yellow, and green rankings reflect accelerated, rolling over to a peak, and well on the decrease death rates, respectively.

We make the following comments:

  • Most countries and states have advanced past the peak of the death rate curve. Some that we have called at the top still need more data to strengthen that assessment
  • The Gaussian model is holding up reasonably well, but we might expect a slower decline than rise as new, but lower density outbreaks are triggered. We will look at final data before adjusting the model.

Next is our familiar table for forecasted total deaths, prevalence (current cases), and incidence (new cases) along with their values per capita (per million people) as well as dates we consider to be the earliest to begin a graduate easing of social distancing. We will continue to call this an easing date and not a safe date to dampen excessive hopefulness.

Assumptions: Mortality factor is estimated as 1.0% for most favorable populations (not yet strained health care system) and up to 2.0% for least favorable populations (strained healthcare system).

We repeat from last week that as a rough rule of thumb the easing date cannot be before the point when the prevalence count drops to less than what it was when the death rate took off. This is because we don’t have a vaccine nor is there sufficient herd immunity (those who have had the disease and developed antibodies) to change the vulnerability to new outbreaks. Roughly the easing date should be about 4-5 weeks after the death peak, the range depending on how severe the outbreak was for a particular population.

Now that the momentum to ease restrictions is gaining momentum and we are sure to initiate this prematurely, we must have a phased approach. The Administration has proposed something that includes many common sense recommendations, e.g., continue to practice good hygiene and advising sick people to stay at home. However, the three-phased approach is lacking in specifics, e.g., “bars may operate with diminished standing-room occupancy,” without defining density or distance requirements. So please read my posting: “11. Recommended Guidelines for Easing of Social Distancing” and please give me your thoughts.

Finally, we provide a new update on the comparison of our forecast of critical values to that of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington (UW), which has emerged as perhaps the leading model for informing our nation on the state of COVID-19 (http://www.healthdata.org/covid/).

We appear to be tracking very closely indicating that there must be components of each model that are similar. We tend to forecast a little earlier from peak rates. As the death rate curve flattens the accuracy of forecasts improve greatly because it is more evident where in the rise and fall cycle a given population is. This is evident as our forecast Total deaths are starting to converge.

2 thoughts on “12. Weekly Update: All Populations are in Recovery”

  1. I want to challenge one of your core assumptions: we are going to have a peak. I think it is possible we do not.

    Everyone else has had a peak, but these countries also implemented serious social distancing and stuck to it. I think the US will be different. I do think there was widespread adoption of these policies in the key areas, but the spread is hitting other areas and US citizens are increasingly not following guidelines (if they ever did). I think it will continue to spread to new areas as well as maintain significant new spreads in previous areas. The US is very large in population and has a large percentage of population of 30%-50% who simply won’t listen to guidelines.

    While we may not get WORSE with a modest amount of social distancing remaining in place, we have seen a constant plateau of 2,000 deaths per day for a few weeks now and that may be the new norm in the US for several more months (if we’re lucky and it doesn’t get worse). More disturbingly, the share of that 2,000 deaths per day is increasingly not NY/NJ but other areas.

    1. The U.S. is way behind but I think it will peak just because every other nation has peaked and I don’t think the resolve of Americans is any less than anywhere else despite the mixed messages being delivered by our Administration. I don’t think it will be several months, but it may be agonizingly long. Even the worst of the states recover and even NY and NJ are showing signs of peaking, but other populations as you say will then get a delayed outbreak. But as I commented in replies before these are lower and lower population densities so they stretch out the sum, but eventually they peter out. One thing for sure, we are not seeing a symmetric rise and fall as was observed in China (but we can’t trust that) and the 1918 Spanish Flu. I will need to modify my model and thinking of a kinetic model with rise and fall rate constants that are not the same.

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