Thursday, July 02, 2020

CDC Updated (July 1st) COVID-19 Hospitalization Forecasts


#15,341

Despite initial hopes that summer would help suppress COVID-19 transmission, yesterday (July 1st)  saw the greatest number of new COVID-19 cases in the United States since the pandemic began, exceeding 50,000 cases for the very first time.

The true number of new infections is unknown, as not every case gets tested. But estimates range anywhere from 5 to 10 times more than are officially reported.  

While we seem to be seeing a younger demographic testing positive this summer - and they appear less likely to develop severe disease and require hospitalization - there are genuine concerns that some hospitals may soon be overwhelmed with patients if these trends continue. 
 
Starting with just two models, 5 weeks ago the CDC began publishing forecasts of COVID-19 hospitalizations 28 days into the future. Today, that ensemble has increased to 7 - and while there is a  wide divergence of opinion - more than half  (n=4) are forecasting a significant increase in hospitalizations by the end of July. 

This compares to last week's forecast, where 3 of 5 models predicted a stable downward trend in hospitalizations.

There remains a 15-fold difference between the high and low estimates of daily hospitalizations 4 weeks downrange, but for the first time  most of the models are clustered on the high side.  Over time we should get a better idea of which of these models are most predictive.

Updated July 1, 2020
 
Interpretation of Forecasts of New Hospitalizations
  • This week, four national forecasts suggest an increase in the number of new COVID-19 hospitalizations per day over the next four weeks, while three other forecasts predict stable numbers or slight declines.
  • On July 25, the forecasts estimate 1,000 to 15,000 new hospitalizations per day.
  • State-level forecasts also show a high degree of variability, which results from multiple factors. Hospitalization forecasts use different sources of data for COVID-19 cases or deaths, with different limitations, and make different assumptions about social distancing.

National Forecasts
 
  • The seven national forecasts show the predicted number of new COVID-19 hospitalizations per day for the next four weeks in the United States.
  • The forecasts make different assumptions about hospitalization rates and levels of social distancing and other interventions and use different methods to estimate the number of new hospitalizations. See models below for details.
State Forecasts

Eight state-level models predicting the number of new hospitalizations were submitted this week. These forecasts show the predicted number of new COVID-19 hospitalizations per day for the next four weeks in each state. Each state forecast uses a different scale, due to differences in the number of new COVID-19 cases occurring per day in each state.

Download forecast data excel  [CSV – 1.8 MB]

Forecast Assumptions

These forecasts make different assumptions about social distancing measures and use different methods and data sets to estimate the number of new hospitalizations. Individual models are described in more detail below.

Social distancing is incorporated into the forecasts in two different ways:
  • The national and state-level forecasts from Columbia University, the COVID-19 Simulator Consortium, the Institute for Health Metrics and Evaluation (IHME), and the Johns Hopkins University Infectious Disease Dynamics Lab (JHU) make assumptions about how levels of social distancing will change in the future.
  • The national and state-level forecasts from the Georgia Institute of Technology, College of Computing, the US Army Engineer Research and Development Center (ERDC), and the University of California, Los Angeles (UCLA), and state-level forecasts from the Los Alamos National Laboratory (LANL) assume that existing social distancing measures in each state will continue through the projected four-week time period.
The rate of new hospitalizations is estimated using three approaches:
  • The forecasts from Columbia University, the COVID-19 Simulator Consortium, ERDC, JHU, LANL, and UCLA assume that a certain fraction of infected people will be hospitalized.
  • The IHME forecast estimates hospitalizations based on numbers of forecasted deaths.
  • The forecast from the Georgia Institute of Technology, College of Computing, uses COVID-19 hospitalization data reported by some states to forecast future hospitalizations.
 

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