March 2020 – Page 2 – COVID-19 Journal

As hospitals scramble to prepare, they are asking the question, just how bad could it get? As I was trying to find answers to help inform our local hospitals, I struck gold with the COVID-19 Hospital Impact Model for Epidemics (CHIME), an online tool developed by the Predictive Healthcare team at UPenn Medicine.

The tool helps project the expected number of daily hospital admissions, intensive care unit (ICU) admissions, and admitted patients in need of a ventilator, as well as admitted patient totals, based on a number of assumptions about the community, hospital system, and spread of the virus. It is not predictive, but rather a tool that could be helpful in planning for the anticipated demand on the local hospital system.

I ran an analysis for Small City, USA. My model assumptions were as follows:

Model Assumptions

1 known case
1 known hospitalization
6 day case doubling time
5% case hospitalization rate
2% case ICU rate
1% case ventilated rate
7 day hospital length of stay (LOS)
9 day ICU LOS
10 day ventilator LOS
50% hospital market share (we have two main hospitals)
65,000 population

The key consideration here is case doubling time. A 6-day case doubling time simulates the spread of COVID-19 unchecked, without any mitigation efforts like social distancing. In other words, we are modeling the worst case scenario, given what we know and where we are today. Here are the results.

Figure 1: Projected number of **daily** COVID-19 admissions

Without mitigation, COVID-19 hospital admissions peak at 56 days (8 weeks) with 18 new admissions per day, including 6 ICU patients, and 3 on ventilators (Figure 1). Because average length of stay is 7 days for each admitted patient and longer for those needing intensive care, the projected total number of admissions on day 56 paints a dire picture.

Figure 2: Projected **total** COVID-19 patients, accounting for arrivals and discharges

At its peak, COVID-19 patients would account for 122 hospital beds in 8-weeks time, with 62 patients in the intensive care unit, and 34 on ventilators. It is unclear whether our hospitals currently have, or will have, the beds, ventilators, supplies, and personnel needed to treat this number of patients (Figure 2). And what does the rest of Small City look like?

Figure 3: The number of infected and recovered individuals in the hospital catchment region at any given moment

At around 9 weeks, without social distancing measures, we would see more than 17,000 cases at the peak of the COVID-19 outbreak. That is nearly 1 in 4 Small City residents (Figure 3).

Social Distancing is the Difference Maker

Now back to that oh-so important case doubling time. If we can add just 2 days to the amount of time it takes for the number of cases to double, from 6 to 8 days, best achieved though social distancing measures, we can push the peak out by 2 weeks and reduce the number of daily hospital admissions by more than 40% (Figure 4).

And the more social distancing the better. If we can reduce social contact by 25%, we see a 65% drop in daily admissions (Figure 5), and the total number of community cases drops from 17,000 to just over 10,000 at peak (Figure 6).

There is a reason why schools are closed, businesses are closed, and we are being ~~asked~~ told to isolate at home. Social distancing works. Without it, we risk overloading our hospitals and putting COVID-19 patients – and healthcare workers – in a very dangerous place.

For more on how social distancing works to slow the spread of COVID-19, check out this Washington Post animation.

Figure 4: Projected number of **daily** COVID-19 admissions, with CDT of 8 days

Figure 5: Projected number of **daily** COVID-19 admissions, at 25% social distancing

Figure 6: The number of infected and recovered individuals in the hospital catchment region at any given moment, at 25% social distancing

LATEST POSTS

Yesterday, our city identified its first case of novel coronavirus 2019 (COVID-19). Earlier in the week, the Mayor, with guidance from the city’s COVID-19 Task Force, implemented a series of protective, social distancing measures including the preemptive closing of schools, dine-in restaurants, playgrounds, fitness centers, and other venues that promote large groups of people. The goal of these measures is to slow the spread of the virus and to give our local hospitals the best chance of keeping up with the expected influx of COVID-19 patients.

We are a small US city of approximately 65,000 people, located just outside of a major metropolitan area. Just under 15% of our citizens are above the age of 65 and, thus, at higher risk for symptoms that would require hospitalization. For those under the age of 65, about 12% do not have health insurance and, thus, may be at risk of having overall poorer health relative to those with better access to healthcare. Initial estimates suggest that without protective measures, at its peak, our city could have as many as 17,000 active cases, or about 1 in 4 people. That is what makes these protective measures so critically vital.

In the days, weeks, and months to come, we will experience something that we haven’t experienced in over 100 years with the COVID-19 pandemic. Every minute of every day will be an opportunity to learn, but also an opportunity to react and respond in ways that can ultimately save lives. This blog will track the day-to-day developments in our city and share information that may be useful to help inform other local health officials and response teams as we experience and combat this, together.