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.