Hospital bed usage and trends in COVID-19 symptoms

By: Kyle Freese, PhD, MPH

Weekly Summary 5/28/2020

First, a quick update on the U.S. COVID-19 situation. 1.6 million cases, roughly 96,000 deaths, and nearly 300,000 recovered.
In my last update, I addressed the question “what should we expect in Arizona during May?”. Now that we are wrapping up the third week of the month, we can evaluate how the state is tracking. As expected, the number of new, confirmed cases has increased. However, in the past 3 weeks Arizona has implemented their “testing blitz”. In 3 weeks, the state has essentially tripled the total number of tests performed statewide. While these efforts are important for gaining insight into the overall prevalence of SARS-CoV-2 in the population, it tells us less about how the incidence of infection is changing over time. Said another way, we cannot confidently remove the effect of increased testing capacity from the trend in new cases. As such, the resulting epidemic curves are less informative if they had been constructed while testing capacity remained high and consistent over an extended period of time.
As more data have become available, it might be more appropriate to look at different measures of healthcare usages to gauge the trend of COVID-19 disease in the population. The Arizona Department of Health Services reports several metrics; when evaluated alongside testing capacity and number of confirmed cases, we gain a more reliable understanding of how the virus is impacting our communities.
The frequency of new hospitalizations due to COVID-19 can provide some insight into the severity of disease in the state. Though illness can be serious even if it does not result in hospitalization, examining the trends in hospitalization from a population standpoint can shed light on the broader trends in how the virus is causing the worst illnesses. From these data alone, it appears that peak hospitalizations occurred in early April and have slowly declined since (Figure 1). Now, these data should not give us a false sense of security; yes, the trend is promising, but this measure is not perfect. It does not capture those who had serious illness but never went to the hospital or those that died from COVID-19 without ever being hospitalized. Nevertheless, the estimates presented in Figure 1 below likely have less misclassification and bias compared with using the number of confirmed cases.

Figure 1: Number of new COVID-19 related hospitalizations in Arizona

The number of new hospitalizations must be viewed within the context of healthcare capacity. Though the number of new hospitalizations is trending downward, hospital bed and ICU usage remains high. As of 21-May, 83% of both, inpatient and ICU beds in Arizona hospitals were being used. This is important for two reasons. First, even if new hospitalizations are decreasing, this does not necessarily mean hospital discharges are occurring at the same rate. The average hospital stay for seasonal influenza related illness is around 5 days. The median length of hospitalization for COVID-19 related illness among survivors? 10-13 days. Prolonged stays can place additional stress on the healthcare system and if inputs (i.e. new hospitalizations) outweigh the outputs (i.e. discharges), the healthcare system can still become overwhelmed. That leads to the second point. A steady, net-positive rate of hospitalizations can lead to healthcare facilities reaching capacity, but with an sudden influx of patients (like the one that would happen with an early second wave of infection), capacity is reached much faster. If a second wave of infection is experienced before the patients from the current wave can be discharged, the healthcare system is in a doubly precarious position; we will start the second wave at a lower capacity of beds than we did with the first wave. And if epidemiologic history has taught us correctly, second waves of pandemics are typically worse than the first. Now is not the time for complacency.

To end on a hopeful note, Figure 2 shows the trend in hospital COVID-like illness (CLI) in Arizona. Since the peak in late March, there appears to have been a decline in both, CLI from the emergency department as well as inpatient facilities. If we can continue this trend through continued preventive action (just because society is starting to open back up does not mean that hand washing and distancing is no longer important), we will be best prepared for future outbreaks.

Figure 2: Trend in percent of emergency department and inpatient visits with COVID-19 like illness (7 day average reported)

References:

https://www.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6

https://www.nytimes.com/article/coronavirus-county-data-us.html

https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-guidance-management-patients.html

https://www.azdhs.gov/preparedness/epidemiology-disease-control/infectious-disease-epidemiology/index.php#novel-coronavirus-home

For additional references, resources, or questions, please email Dr. Kyle Freese at kyle_freese@stchome.com