CDPHE and CSPH: New modeling data shows plateauing hospitalizations and a slight upward trend in Colorado’s infection rate

REMOTE, Sept. 16: The Colorado Department of Public Health and Environment and Colorado School of Public Health released a new modeling report that indicates the spread of SARS-CoV-2 was reduced for much of July and August, leading to declines in hospitalizations and infections. However, in recent weeks, the estimated effective reproductive number has increased while hospitalizations have plateaued.

The latest modeling provides projections based on COVID-19 hospital census data to characterize the current status of the COVID-19 epidemic in Colorado, and the collective impact of efforts to reduce the spread of the SARS-CoV-2 virus. It also provides projections based on various policy scenarios around physical distancing, mask-wearing, and case detection, and containment. The models are based on Colorado data and assumptions based on the current state of the science.

Key findings from the report:

  • COVID-19 hospitalizations have been decreasing since mid-July. This decline has slowed and hospitalizations appear to be at a plateau.
  • The estimated effective reproductive number has increased following an upward trend over recent weeks. The current effective reproductive number is estimated to be between 0.93 and 1.14. Due to lags between infection and hospitalizations, this reflects transmission occurring through late-August (approximately August 25).
  • The model-estimated number of infectious individuals in Colorado remains relatively low. The model-estimated rate of new infections as well as reported cases had been declining since mid-July, but the decline now appears to be leveling off.
  • Our current estimate of physical distancing is between 65% and 72% (65% for the week of August 17-25 and 72% during the three-week period August 3-25). If physical distancing remains at 65%, we will begin to see gradual growth in cases and/or hospital demand.

The Colorado School of Public Health (ColoradoSPH) assembled the expert group that works with the state on modeling projections. The group includes modeling scientists at the ColoradoSPH and the University of Colorado School of Medicine at the CU Anschutz Medical Campus, as well as experts from the University of Colorado Boulder, University of Colorado Denver, and Colorado State University. 

All modeling reports are available on the Colorado School of Public Health’s COVID-19 website. 

The state will continue to review data and model findings as the pandemic continues to inform future policy decisions. 

CDPHE and CSPH: New modeling data shows plateauing hospitalizations and a slight upward trend in Colorado’s infection rate

Colorado School of Public Health: State releases new modeling findings

DENVER (April 6, 2020): The state health department received additional modeling results from an expert group of public health scientists today. The Colorado School of Public Health (ColoradoSPH) assembled the expert group, which relies on expertise from modeling scientists at ColoradoSPH and the University of Colorado School of Medicine at the CU Anschutz Medical Campus, as well as experts from the University of Colorado Boulder and University of Colorado Denver. The models produced by the expert group are local, meaning models are based on Colorado data and assumptions apply specifically to Colorado, not national assumptions.

Several key staff from the Colorado Department of Public Health and Environment spoke about the model’s results earlier today in a press conference that was broadcast for the public. The findings demonstrate the effectiveness of physical distancing in phase 1 — cancelling mass gatherings, and the closing of bars and schools — and the data provide projections for effectiveness of phase 2 physical distancing, including the Governor’s Stay-at-Home order through April 26.

The model results show that with physical distancing, the spread of COVID-19 has slowed in Colorado, but case counts are still increasing.

The Colorado model is now available to the public, as are the presentation slides.

The state will continue to review data and model findings as the pandemic continues to inform future policy decisions. 

Continue to stay up to date by visiting covid19.colorado.gov.

Colorado School of Public Health: State releases new modeling findings

CDPHE: State provides COVID-19 modeling data

DENVER (April 5, 2020): The state today released additional COVID-19 modeling data to the public. Governor Jared Polis first provided an in-depth analysis of the data during a press conference on March 27. The state will continue to review data as it evolves to inform future policy decisions.

The modeling data was produced by an expert team that the Colorado School of Public Health (ColoradoSPH) assembled to assist the Colorado Department of Public Health and Environment (CDPHE) in understanding the potential course of the pandemic in Colorado. 

Drawing on expertise from the ColoradoSPH and the University of Colorado School of Medicine at the CU Anschutz Medical Campus, and the University of Colorado in Denver and Boulder, a team of volunteer experts modeled the pandemic using approaches tailored to Colorado, updating the modeling as the disease continues to spread in the state.

The team uses a fundamental approach: the SEIR model. The basics of the models are intuitive: prior to infection, individuals are susceptible (S) and once exposed (E) and infected (I) they are contagious, whether symptomatic or asymptomatic; those infected may recover and become resistant (R) or become sufficiently ill to need hospitalization and possibly critical care and to die. This standard model is thus abbreviated as the SEIR model. 

Another important number in the model is the reproductive number (R0), that is, the average number of new cases generated per infected person at the beginning of the outbreak. (The Governor has referred to this number as the “R naught.”) If that number exceeds one then the infection will spread. Various figures for R0 have been reported at the start of the COVID-19 pandemic from different parts of the world, ranging from about 2 to 5. The reproductive number depends, in part, on the frequency of contacts between infected and uninfected individuals. The goal of social distancing, which we are all experiencing now, is to reduce these contacts and lower the reproductive number with a target value below one so that contagion ends. A critical question is: How much social distancing is needed to control the epidemic, and how long does it need to be in place?

The tables below provide two sets of numbers provided to CDPHE and the Governor’s Office. The numbers provided are for critical indicators and show the variation by the value of R0 at the beginning of the outbreak and the effectiveness of social distancing at reducing the contact rate, ranging from none to an 80% reduction. When these numbers were calculated, the team found that the R0 value for Colorado was likely above 3. To capture the uncertainty in R0 and the effectiveness of social distancing, estimates are provided for a range of values.

Model R0 3.5 4.0 with SD 0 to 80

Model R0 3.0 4.0 SD 0 to 60

The Colorado modeling team has continued to refine its models as the data accumulate on the course of the pandemic. There are other models that provide estimates for Colorado, but those models are not as closely linked to the state’s data.

Continue to stay up to date by visiting covid19.colorado.gov.

CDPHE: State provides COVID-19 modeling data