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| 4 Week COVID-19 Deaths Forecast For State of Florida |
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The late George E. P. Box (18 October 1919 – 28 March 2013) - Professor Emeritus of Statistics at the University of Wisconsin - is often credited with coining the familiar adage:
“All models are wrong, but some models are useful.”While imperfect, we use computer models every day to try to mathematically simulate real- world events; everything from climate change to Hurricane Forecasting.
Despite their sophistication, nearly 20 million Floridians who found themselves in the forecast cone of Hurricane Dorian last year - only to see it stall, then veer away - can attest that computer models are not writ in stone.
Pandemic models often come up in this blog, and while necessary for planning purposes, need to be taken with a sizeable grain of salt.
But, as everyone with cabin fever knows, strong public health measures, including school and business closures, social distancing, and stay-at-home orders have made a huge difference in the Case Attack Rate (CAR) and death toll from COVID-19.
Yesterday the CDC released new modeling - based on various levels of social distancing - looking at probable pandemic deaths in the United States over the next 4 weeks for all 50 states.
Pandemic models often come up in this blog, and while necessary for planning purposes, need to be taken with a sizeable grain of salt.
In late summer of 2014, modelers published a worst case estimate of between 550,000 and 1.4 million Ebola cases in Liberia and Sierra Leone by the end of January - if interventions were not implemented - (see MMWR: Estimating The Future Number of Cases In The Ebola Epidemic).Interventions were taken, however, and the total number of Ebola cases came in somewhere under 30,000 cases. Horrific, yes - but less than 1/10th of the lowest estimate. We've seen similar estimates of deaths in the United States from COVID-19 - had interventions not been taken - that exceeded 2 million.
But, as everyone with cabin fever knows, strong public health measures, including school and business closures, social distancing, and stay-at-home orders have made a huge difference in the Case Attack Rate (CAR) and death toll from COVID-19.
Yesterday the CDC released new modeling - based on various levels of social distancing - looking at probable pandemic deaths in the United States over the next 4 weeks for all 50 states.
Depending on the models used, that death toll could range from roughly 60,000 to over 150,000 people.
We've two updates, published by the CDC provide the details on their COVID-19 forecasting. First, a description of the models used. (Note: All models assume mitigation efforts will remain in place until the end of May).
Follow the link in the State Forecasts to view each individual state.
COVID-19 Forecasts for the United States
Why Forecasting COVID-19 Deaths in the US is Critical
CDC is responding to a pandemic of coronavirus disease 2019 (COVID-19) caused by a novel coronavirus, SARS-CoV-2, that is spreading from person to person. The federal government is working closely with state, tribal, local, and territorial health departments, and other public health partners, to respond to this situation. Forecasts of deaths will help inform public health decision-making by projecting the likely impact in coming weeks.
What the Forecasts Aim to Predict
Forecasts based on the use of statistical or mathematical models (subsequently referred to as “models”) aim to predict changes in national and state level cumulative reported COVID-19 deaths for the next four weeks. Forecasting teams predict numbers of deaths using different types of data (e.g., COVID-19 data, demographic data, mobility data), methods (see below), and estimates for the impacts of interventions (e.g. social distancing, use of face coverings).
Working to Bring Together Forecasts for COVID-19 Deaths in the U.S.
CDC works with partners to bring together weekly forecasts for COVID-19 deaths in one place. These forecasts have been developed independently and shared publicly. It is important to bring these forecasts together to help understand how they compare with each other and how much uncertainty there is about what may happen in the upcoming four weeks.
Columbia University
Model names: CU 20% contact reduction, CU 30% contact reduction, CU 40% contact reduction
Intervention assumptions
These models are based on assumptions of reducing the number of contacts per case. Three different adaptive scenarios of contact reduction are projected: 20%, 30%, and 40% contact reduction in US counties with at least 10 cases. Additional reductions are implemented with additional new cases, and all social distancing interventions remain in place until the end of the projection.
Methods
Metapopulation SEIR model
Institute for Health Metrics and Evaluation
Model name: IHME
Intervention assumptions
This model assumes social distancing stays in place until the pandemic, in its current phase, reaches the point when COVID-19 deaths are less than 0.3 per million people. Based on these latest projections, IHME expects social distancing measures to be in place through the end of May.
Methods
Non-linear mixed effects curve-fitting
Los Alamos National Laboratory
Model name: LANL
Intervention assumptions
Currently implemented interventions and the corresponding reductions in transmission will continue to be upheld in the future, resulting in an overall decrease in the growth rate of COVID-19. Over the course of the forecast, the model assumes that the growth will decrease over time.
Methods
Statistical dynamical growth model accounting for population susceptibility
Northeastern
Model name: MOBS (Laboratory for the Modeling of Biological + Socio-technical Systems)
Intervention assumptions
The projections assume that social distancing policies in place at the date of calibration are extended for the future weeks.
Methods
Metapopulation, age-structured SLIR model
Additional Resources:
COVID-19 Forecast
Follow the link in the State Forecasts to view each individual state.
COVID-19 Forecasts
Last updated April 19, 2020
National Forecast
These forecasts show cumulative reported COVID-19 deaths since February and forecasted deaths for the next four weeks in the United States.
The IHME and MOBS models assume existing social distancing measures continue through the forecasting period while the CU models assume different levels of social distancing.
State Forecasts
State level forecasts show observed and forecasted state level cumulative COVID-19 deaths in the US.
Forecasts fall into one of three categories
- The LANL model does not explicitly model the effects of individual social distancing measures but assumes that implemented interventions will continue to be upheld in the future resulting in decreased growth.
- The IHME and MOBS_NEU models are conditional on existing social distancing measures continuing through the projected time−period.
- The CU models make different assumptions about the effectiveness of current social distancing interventions.
Download state forecasts pdf icon[PDF – 57 KB]
Download model data excel icon[XLS – 106 KB]
Additional Resources:
COVID Cases, Data, and Surveillance
FAQ: COVID-19 Data and Surveillance
