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Model Estimates of Cases and Hospitalizations in Santa Clara County

 

On April 7, 2020, County Health Officer Dr. Sara Cody presented to the Board of Supervisors and the public information on modeling regarding various metrics related to the spread of COVID-19 in our community and the anticipated surge in hospitalizations. These models were prepared through a collaboration between Public Health Department epidemiologists and infectious disease modeling experts at Stanford University’s School of Medicine. These models were developed using data from our County including current case counts, current cases hospitalized, and information that we know about the clinical course of cases here and elsewhere. They provide a projection of possible outcomes, and a range of uncertainty around those outcomes, their timing and magnitude. While there is a significant degree of uncertainty around these projections (and all others being prepared by experts around the world), these estimates inform our planning, preparedness, and our understanding of the impact of public health interventions.

Graphics providing a snapshot of this modeling as of April 7, 2020 are provided below:

COVID-19 Cases (Projected) in Santa Clara County

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Chart: COVID-19 projected cases 

  • Had a Shelter in Place Order not been put in place on March 16th, we expect we would have had approximately 50,000 cases of COVID-19 in our County by May 1st. The red line above reflects the number of cases we expect we would have had absent a Shelter in Place Order.
  • Because of the Shelter in Place Order, our confirmed cases are already lower than the projected number of cases we expect we would have now without the Order. We believe we are now in the very early stages of the “flattening of the curve” the Order was designed to achieve.
  • Looking forward in time, the model estimates that by May 1st our case counts are likely to be far lower than they would have been without the Shelter in Place Order.
  • These are only models, however, and many factors can change future outcomes, including our continued ability to maintain the shelter in place. These projections should also be interpreted knowing we still have limited testing capacity.
  • However, our models strongly suggest that our Shelter in Place order has had a significant impact on what would have been more significant exponential growth in cases.

Acute Hospital Bed Demand (Projected) in Santa Clara County to May 27th

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Chart: COVID-19 projected acute hospital demand 

  • ​Our models regarding hospitalizations due to COVID-19 likewise show the impact of the Order to Shelter in Place. The graph above shows, via the red line, what we expect the number of hospitalized persons with COVID-19 would have been without the Shelter in Place Order, and the blue line shows what we expect the number of hospitalized patients will be given the Shelter in Place Order we issued.
  • The red line shows that without the Order, our acute hospital bed capacity would likely have been exceeded by mid-April; and by the end of April our increased hospital surge bed capacity would likely have been exceeded as well.
  • However, because the Order slowed transmission, we hope to have sufficient capacity to treat all COVID-19 patients through at least mid-May, which is as far out as our and other models can reasonably provide projections.
  • This flattening of the curve gives our community much needed additional time to increase our surge capacity.

​Doubling Time of COVID-19 Cases in Santa Clara County

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Chart: Doubling time of COVID-19 cases 

  • One of the most important indicators of a slowing of the spread of COVID-19 is what we call the “doubling rate” – how many days it takes for the number of cases to double.
  • A lower doubling rate (also known as “doubling time”) means that the disease is spreading rapidly; a higher doubling rate means it is taking longer for the number of cases to double, as the spread slows down.
  • In early March, our case numbers doubled approximately every 3 days. Now our doubling rate is somewhere around 15 days.
  • This means that the rate of spread has slowed thanks to our residents complying with the Shelter in Place Order.
  • This slowing is essential for us to continue our hospital surge capacity.
  • Increasing the doubling rate, slowing the spread, and increasing our hospital surge capacity is what will save many lives in our community.​

​Every person’s individual actions to comply with the Shelter in Place Order contribute to whether the spread of COVID-19 slows down as we hope, or instead spreads rapidly. We hope and expect that everyone in our community will do their part to comply with the Order, reduce frequency and duration of any contacts with others to the maximum extent possible, and contribute to the community-wide effort to saves lives.

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Last updated: 5/12/2020 12:25 PM