Estimated Fraction of Incidental COVID Hospitalizations in a Cohort of 250 High-Volume Hospitals Located in 164 Counties

Incidental COVID infections appear to be a nontrivial fraction of all COVID-positive hospitalized patients. In the aggregate, however, the burden of patients admitted for complications of their viral infections appears to be far greater.

Estimated Fraction of Incidental COVID Hospitalizations in a Cohort of 250 High-Volume Hospitals Located in 164 Counties
Whiskers-on-Box Plots of Weekly Confirmed COVID Incidence per 100,000 Population in the 164 Counties Containing the 250 Study Hospitals, Weeks Ending December 19, 2021 Through January 9, 2022. For each week, the 5th, 25th, 50th, 75th, and 95th percentiles are superimposed upon the individual county-specific datapoints. A total of 11 datapoints with zero incident cases are omitted from the first two weeks. Source: https://www.medrxiv.org/content/10.1101/2022.01.22.22269700v1

New Pre-Print Posted on MedRxiv.

Scattered reports have suggested that as many as one-half of all hospital inpatients identified as COVID-positive are incidental cases who were admitted primarily for reasons other than their viral infections. To date, however, there are no systematic studies of a representative panel of hospitals based on pre-established criteria for determining whether an individual patient was in fact admitted as a result of the disease. To fill this gap, we developed a formula to estimate the fraction of incidental COVID hospitalizations that relies upon measurable, population-based parameters.

Among COVID-positive hospitalized patients, 15.2% were estimated to be incidental infections. Across individual counties, the median fraction of incidental COVID hospitalizations was 13.7%, with an interquartile range of 9.5 to 18.4%

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Florida COVID-19 Hospital Admissions may Have Reached a Peak, or Maybe Not

There is still no widely accepted theory that explains why a wave triggered by a new variant of SARS-CoV-2 should have only a single peak.

We relied on data from the U.S. Department of Health and Human Services to track combined adult and pediatric hospital admissions for confirmed COVID-19 among all Florida hospitals. The horizontal time axis is measured in days from the estimated first appearance of each variant. See Technical Notes below for details.

We further update our ongoing comparison of the hospitalization curves for the Delta and Omicron waves in Florida. While statewide daily hospital admissions accelerated much more rapidly during the current Omicron wave, the Omicron curve appears to have reached a peak and may be trending downward.

Admissions appear to have peaked at about 2,200 on January 12 , just below the high point seen during this past summer’s Delta wave.

We stress that this is purely an empirical observation. There is no widely accepted theory that explains why a wave of infections triggered by the emergence of a new variant of SARS-CoV-2 should have only a single peak.

We will continue monitor trends in Florida COVID-19 hospital admissions.

Technical Notes

As we’ve repeatedly noted, we do not have data on the variant underlying each hospital admission. Still, according to the most recent CDC report on state-specific variant proportions, 99.7% of recent SARS-CoV-2 samples sequenced in the U.S. region covering Florida were attributable to the Omicron variant.

We have estimated the initial appearance of the Delta variant as June 10, 2021. There are reports that the variant was in fact detected by late May. If we translated the time axis for Delta to the right, however, the Omicron-related hospitalization curve would be running even further ahead of its predecessor.

The calculations in the figure are derived from COVID-19 Reported Patient Impact and Hospital Capacity by State Timeseries, maintained by the U.S. Department of Health and Human Services. The daily counts represent the daily sums of two variables for all Florida hospitals combined:

  • previous_day_admission_adult_covid_confirmed: Number of patients who were admitted to an adult inpatient bed on the previous calendar day who had confirmed COVID-19 at the time of admission in this state
  • previous_day_admission_pediatric_covid_confirmed: Number of pediatric patients who were admitted to an inpatient bed, including NICU, PICU, newborn, and nursery, on the previous calendar day who had confirmed COVID-19 at the time of admission in this state

Some commentators have expressed a general concern that COVID-19 hospitalization counts include patients admitted for unrelated reasons who incidentally tested positive. We are now preparing an article on this important issue.

Florida COVID-19 Hospital Admissions may be Approaching a Peak

Statewide admissions are now hovering at about 2,150 per day, just below the high point seen during this past summer’s Delta wave.

We relied on data from the U.S. Department of Health and Human Services to track combined adult and pediatric hospital admissions for confirmed COVID-19 among all Florida hospitals. The horizontal time axis is measured in days from the estimated first appearance of each variant. See Technical Notes below for details.

We further update our ongoing comparison of the hospitalization curves for the Delta and Omicron waves in Florida. While daily hospital admissions have accelerated much more rapidly during the current Omicron wave, the Omicron curve appears to be decelerating.

We will continue monitor trends in Florida COVID-19 hospital admissions.

Technical Notes

As we’ve repeatedly noted, we do not have data on the variant underlying each hospital admission. Still, according to the most recent CDC report on state-specific variant proportions, 99.0% of recent SARS-CoV-2 samples sequenced in the U.S. region covering Florida were attributable to the Omicron variant.

We have estimated the initial appearance of the Delta variant as June 10, 2021. There are reports that the variant was in fact detected by late May. If we translated the time axis for Delta to the right, however, the Omicron-related hospitalization curve would be running even further ahead of its predecessor.

The calculations in the figure are derived from COVID-19 Reported Patient Impact and Hospital Capacity by State Timeseries, maintained by the U.S. Department of Health and Human Services. The daily counts represent the daily sums of two variables for all Florida hospitals combined:

  • previous_day_admission_adult_covid_confirmed: Number of patients who were admitted to an adult inpatient bed on the previous calendar day who had confirmed COVID-19 at the time of admission in this state
  • previous_day_admission_pediatric_covid_confirmed: Number of pediatric patients who were admitted to an inpatient bed, including NICU, PICU, newborn, and nursery, on the previous calendar day who had confirmed COVID-19 at the time of admission in this state

Some commentators have expressed a general concern that COVID-19 hospitalization counts include patients admitted for unrelated reasons who incidentally tested positive. We will have more to say about the issue of incidental COVID-19 hospitalizations in a future article.

Florida Hospital Emergency Department Visits for COVID-19 Surpass Last Summer’s Delta Peak

Hospital ED visits for COVID-19 are a more informative indicator of disease burden than total reported cases.

Weekly Florida Hospital Emergency Department Visits for COVID-19. Each frame of the animation shows one week with the indicated ending date. Each data point is a hospital. The size of the data point reflects the number of emergency department visits for COVID-19. Source: COVID-19 Reported Patient Impact and Hospital Capacity by Facility (HHS).

The above animation shows the evolution of emergency department visits for COVID-19 during five successive weeks, from the week ending 12/3/21 to the week ending 12/31/21. Each data point represents one hospital, and its size reflects the number of reported ED visits.

Florida Hospital Emergency Department Visits for COVID-19 During the Week Ending 12/31/21. The five hospitals with the highest volume of ED visits are specifically identified, along with the number of reported visits. For further details, see animation above.

The map above is an annotated version of the last frame of the animation, corresponding to ED visit for COVID-19 during week ending 12/31/21. Specifically indicated are the five hospitals with the highest number of ED visits.

Hospital ED visits for COVID-19 approached 75,000 during the week ending 12/31/21, overtaking the Delta peak of 62,100 during the week ending 8/13/21.

Weekly Emergency Department Visits for COVID-19 for All Florida Hospitals. Source: COVID-19 Reported Patient Impact and Hospital Capacity by Facility (HHS).

The graph above charts ED visits to Florida hospitals for COVID-19 for each week from the week ending 6/25/21 through the week ending 12/31/21. We see a marked surge during December with the emergence of the Omicron variant. The total volume of 74,660 ED visits for COVID-19 during the week ending 12/31/21 has surpassed the peak volume of 60,777 ED visits attained during the Delta wave of last summer.

For every 100 ED visits for COVID-19, there are now 15 hospital admissions.

Hospital Admissions for COVID-10 per 100 ED Visits for COVID-19 for All Florida Hospitals. Source: COVID-19 Reported Patient Impact and Hospital Capacity by Facility (HHS).

This graph shows the number of hospital admissions for COVID-19 per 100 ED visits for COVID-19. As discussed in an earlier article, we regard this ratio as one indicator of disease severity. While the week ending 12/31/21 saw 15.5 hospital admissions for COVID-19 per 100 ED visits, this indicator remains below the peak of 25.0 admissions per 100 ED visits seen for the week ending 8/13/21 during the Delta wave.

Why ED Visits Are a More Informative Indicator Than Total Reported COVID-19 Cases

The widespread use of home-based rapid tests has raised doubts about the adequacy of publicly reported case counts. There is a growing sentiment that we need new sentinel indicators of disease burden. Emergency department visits may be just the indicator we’re looking for.

When it comes to the detailed geography of COVID-19 spread throughout the state, our maps of hospital-specific ED visit volume are more informative than the coarse, county-based maps that are frequently posted.

What’s more, the under-reporting bias in case-based indicators of COVID-19 burden has become increasingly correlated with income. As the demand for rapid home-based tests expands in the face of a limited supply, the market price of a rapid tests rises. As the market price continues to rise, rapid tests become a luxury good. They are consumed disproportionately by higher income consumers. That means those areas with higher incomes will suffer from even more under-counting.

As an indicator of the evolution of Omicron in the state, ED visits for COVID-19 do have their own potential biases. Florida has a notably high concentration of uninsured individuals, who may preferentially seek the ED simply to get tested. Large hospitals with emergency departments may serve wide geographic areas. Residents from outside Orange County may travel to the two Orlando-based hospital EDs identified in our map.

Still, emergency department visits quite likely track cases of Omicron infection that are more severe than the self-limited syndrome of sore throat, stuff nose, headache, fever, chills, body aches and fatigue. At the very least, they capture patients who are more seriously concerned about their symptoms.

Technical Notes

The data were derived from COVID-19 Reported Patient Impact and Hospital Capacity by Facility, posted by the U.S. Department of Health and Human Services (HHS). The database is updated weekly. The most recent update, on which this article is based, covers the week ending 12/31/21. An obvious disadvantage of this data source is the 11-day lag between the end of the reporting period and the date of posting.

The data on emergency department visits for COVID-19 are based upon the variable previous_day_covid_ED_visits_7_day_sum, defined as “Sum of total number of ED visits who were seen on the previous calendar day who had a visit related to COVID-19 (meets suspected or confirmed definition or presents for COVID diagnostic testing – do not count patients who present for pre-procedure screening) reported in 7-day period.”

We calculated hospital admissions for COVID-19 as the sum of two variables:

  • previous_day_admission_adult_covid_confirmed_7_day_sum, defined as “Sum of number of patients who were admitted to an adult inpatient bed on the previous calendar day who had confirmed COVID-19 at the time of admission reported in the 7-day period.”
  • previous_day_admission_pediatric_covid_confirmed_7_day_sum, defined as “Sum of number of pediatric patients who were admitted to an inpatient bed, including NICU, PICU, newborn, and nursery, on the previous calendar day who had confirmed COVID-19 at the time of admission.”

Both of these definitions are confined to admitted patients who were diagnosed with confirmed COVID-19 at the time of admission, and thus tend to attenuate the potential problem of so-called incidental admissions.

The maps were based upon the geocodes (longitude and latitude) of each hospital, which were already included in the HHS database. We relied on the Texas A&M interactive geocoding website to fill in the missing geocodes for 18 hospitals. The size of each point was based upon the weighting scheme built into the Stata scatter command.

Critical Staffing Shortages in U.S. Hospitals Continue to Rise

Nearly one in four hospital beds is now located in a hospital reporting a critical staffing shortage.

We analyzed all U.S. hospitals reported by the Department of Health and Human Services. (HHS) The data, originally reported on a daily basis, are aggregated by week. The percentages of all reporting hospitals in each state are weighted by their inpatient bed capacity. HHS appears to rely on each hospital’s self-report of a critical staffing shortage.

This post continues to update our earlier summary of trends in U.S. hospital staffing. During the Delta wave in the United States, the percentage of hospitals reporting critical staffing shortages rose from 12 to 19 percent. Even as hospital admission rates declined in October and November, the critical staffing percentage remained elevated at 19 percent. Over the past four weeks, as the Omicron variant has begun to spread, this percentage has increased to 23.2 percent.

To determine each data point in the figure, we first ascertained the percentage of hospitals in each state reporting a critical staffing shortage, as reported by the Department of Health and Human Services. We then computed the weighted average across all states, where the weights were each state’s inpatient bed capacity. During the week ending January 7, 2022, we’ve thus calculated that 23.2 percent of all U.S. hospital beds were located in a hospital reporting a critical staffing shortage.

Trends in staffing shortages vary across states. Below we plot the percentage of hospitals with critical staffing shortages in two of the hardest hit states: New Mexico and Rhode Island.

Weekly percentages of hospitals reporting critical staffing shortages in New Mexico and Rhode Island from the week ending 5/28/21 to the week ending 1/7/22. Data source: HHS.

The critical staffing shortage percentage in New Mexico has increased steadily from 24.9 during the week ending May 28 to 52.3 during the most recent reporting week ending January 7. By contrast, the proportion of Rhode Island hospitals with a critical staffing shortage shot up to about 50 percent with the emergence of the Delta wave in August and has remained at that level.

Vaccine Mandates are Unlikely to be the Primary Cause.

Some have contended that vaccine mandates are contributing to the emerging shortage of healthcare workers. But there is little concrete evidence to back up this contention. While a small minority of healthcare employees have chosen to leave their jobs, the vast majority have opted for vaccine protection. At large healthcare systems like Houston Methodist, Truman Medical Centers/University Health in Kansas City, the North Carolina hospital system, Advocate Aurora Health in Chicago, Mount Sinai Health System in New York, St. Claire Regional Medical Center in Kentucky, and Henry Ford Health System in Detroit, less than 1 percent of employees have had to be let go.

The Labor Market for Skilled Nursing Care was Already Tight.

Still others have pointed to the increasing fees charged by traveling nurses and nurse staffing agencies to compensate for growing vacancies among nurse employees. The plain fact, however, is that the tight labor market for hospital-based nursing care predated the COVID-19 pandemic. Annual turnover among hospital-based registered nurses was already up to 15.9% in 2019 and increased to 18.7% in 2020.

It’s All About Pandemic Burnout.

Far and away the most critical determinant of rising staff shortages has been burnout and peritraumatic stress among healthcare workers, with more nurses leaving their employment as the pandemic drags on. While burnout among frontline healthcare workers has always been a serious problem, the percent of surveyed hospitals reporting 10% or more vacancies for RNs abruptly rose from 23.7% in 2019 to 31.8% in 2020 to 35.8% by early 2021.

The evidence of burnout among frontline workers is overwhelming not only in the U.S., but many other healthcare systems, including China during the initial Wuhan outbreak. The president of the American Nurses Association recently asked the U.S. Secretary of Health and Human Services to declare a national nursing shortage crisis. A national strategy to address healthcare worker burnout as been repeatedly urged.

We’re talking about continuous exposure to traumatic stress from extended hours, time away from family, near-continuous use of personal protective equipment, fear of personally contracting COVID-19, loss of patients with whom workers have become emotionally attached, and the rising frequency of medical errors as emergency rooms and ICUs fill up. We’re talking not only about ordinary job burnout, but also compassion burnout.

The anti-vaccination movement is driven in part by conspiracy theories that sow doubt about the integrity of medical professionals. Has the resulting loss of confidence caused some healthcare workers to experience a disconnect from their beliefs in the value of their work?

Stay Tuned.

We will continue to follow the aggregate U.S. hospital staffing situation as the Omicron wave plays out.

Florida COVID-19 Hospital Admissions Approaching This Past Summer’s Delta Peak

Daily admissions to Florida hospitals for confirmed adult and pediatric cases continue to double every 6.7 days, now at nearly three times the daily admissions registered at the same point during this past summer’s Delta wave.

We relied on data from the U.S. Department of Health and Human Services to track combined adult and pediatric hospital admissions for confirmed COVID-19 among all Florida hospitals. The horizontal time axis is measured in days from the estimated first appearance of each variant. See Technical Notes below for details.

We further update our comparison of the hospitalization curves for the Delta and Omicron waves in Florida. By day 15 from the initial appearance of each variant, statewide confirmed COVID-19 admissions among adults and children combined were running at about 250 per day. By day 36, however, Delta-wave admissions were 734, while Omicron-wave admissions have reached 2009. That’s nearly three times the number of admissions registered at the same point during this past summer’s wave.

Log-linear regressions on the data points from days 10 to 34 now give doubling times of 20.6 days for Delta and 6.72 days for Omicron. (The 95% confidence interval for the Omicron doubling time is 6.28 – 7.27 days.) As we have repeatedly stressed, these early findings do not necessarily mean that the Omicron curve will reach the Delta peak of 2,360 statewide hospital admissions attained on August 17, 2021 (that is, day 68 from initial appearance).

Hospitalization Rates Matter.

Public officials and some commentators have noted that COVID-19 hospitalization rates are not rising nearly so fast as total case counts. The fact that hospitalization-to-case ratios are now lower than during the past summer’s wave has been highlighted as favorable news. With rapid home-based COVID-19 tests now in abundance, it is unclear what case counts reported by public health departments are supposed to represent.

We continue to focus here on severe disease and its impact on our already stressed healthcare system.

Technical Notes

As we’ve repeatedly noted, we do not have data on the variant underlying each hospital admission. Still, according to the most recent CDC report on state-specific variant proportions, 82.4% of recent SARS-CoV-2 samples sequenced in the U.S. region covering Florida were attributable to the Omicron variant.

We have estimated the initial appearance of the Delta variant as June 10, 2021. There are reports that the variant was in fact detected by late May. If we translated the time axis for Delta to the right, however, the Omicron-related hospitalization curve would be running even further ahead of its predecessor.

The calculations in the figure are derived from COVID-19 Reported Patient Impact and Hospital Capacity by State Timeseries, maintained by the U.S. Department of Health and Human Services. The daily counts represent the daily sums of two variables for all Florida hospitals combined:

  • previous_day_admission_adult_covid_confirmed: Number of patients who were admitted to an adult inpatient bed on the previous calendar day who had confirmed COVID-19 at the time of admission in this state
  • previous_day_admission_pediatric_covid_confirmed: Number of pediatric patients who were admitted to an inpatient bed, including NICU, PICU, newborn, and nursery, on the previous calendar day who had confirmed COVID-19 at the time of admission in this state

Some commentators have expressed a general concern that COVID-19 hospitalization counts include patients admitted for unrelated reasons who incidentally tested positive. Since confirmation of a COVID-19 diagnosis is made by PCR test results that are not immediately available at the time of admission, it is unlikely that the calculations in our figure above suffer from such a potential bias.

We will have more to say about the issue of incidental COVID-19 hospitalizations in a future article.

Florida COVID-19 Hospital Admissions Show No Signs of Slowing, Continue to Outpace Last Summer’s Delta Wave

Daily admissions to Florida hospitals for confirmed adult and pediatric cases continue to double every 6.7 days.

We relied on data from the U.S. Department of Health and Human Services to track combined adult and pediatric hospital admissions for confirmed COVID-19 among all Florida hospitals. The horizontal time axis is measured in days from the estimated first appearance of each variant. See Technical Notes below for details.

We further update our comparison of the hospitalization curves for the Delta and Omicron waves in Florida. By day 15 from the initial appearance of each variant, statewide confirmed COVID-19 admissions among adults and children combined were running at about 250 per day. By day 34, however, Delta-wave admissions were 672, while Omicron-wave admissions have reached 1620. That’s nearly 2.5 time the number of admissions registered at the same point during this past summer’s wave.

Log-linear regressions on the data points from days 10 to 34 now give doubling times of 20.6 days for Delta and 6.71 days for Omicron. (The 95% confidence interval for the Omicron doubling time is 6.21 – 7.33 days.) As we have repeatedly stressed, these early findings do not necessarily mean that the Omicron curve will reach the Delta peak of 2,360 statewide hospital admissions attained on August 17, 2021 (that is, day 68 from initial appearance).

Hospitalization Rates Matter.

Public officials and some commentators have noted that COVID-19 hospitalization rates are not rising nearly so fast as total case counts. The fact that hospitalization-to-case ratios are now lower than during the past summer’s wave has been highlighted as favorable news. With rapid home-based COVID-19 tests now in abundance, it is unclear what case counts reported by public health departments are supposed to represent.

We continue to focus here on severe disease and its impact on our already stressed healthcare system.

Technical Notes

As we’ve repeatedly noted, we do not have data on the variant underlying each hospital admission. Still, according to the most recent CDC report on state-specific variant proportions, 82.4% of recent SARS-CoV-2 samples sequenced in the U.S. region covering Florida were attributable to the Omicron variant.

We have estimated the initial appearance of the Delta variant as June 10, 2021. There are reports that the variant was in fact detected by late May. If we translated the time axis for Delta to the right, however, the Omicron-related hospitalization curve would be running even further ahead of its predecessor.

The calculations in the figure are derived from COVID-19 Reported Patient Impact and Hospital Capacity by State Timeseries, maintained by the U.S. Department of Health and Human Services. The daily counts represent the daily sums of two variables for all Florida hospitals combined:

  • previous_day_admission_adult_covid_confirmed: Number of patients who were admitted to an adult inpatient bed on the previous calendar day who had confirmed COVID-19 at the time of admission in this state
  • previous_day_admission_pediatric_covid_confirmed: Number of pediatric patients who were admitted to an inpatient bed, including NICU, PICU, newborn, and nursery, on the previous calendar day who had confirmed COVID-19 at the time of admission in this state

Some commentators have expressed a general concern that COVID-19 hospitalization counts include patients admitted for unrelated reasons who incidentally tested positive. Since confirmation of a COVID-19 diagnosis is made by PCR test results that are not immediately available at the time of admission, it is unlikely that the calculations in our figure above suffer from such a potential bias.

If hospitals were backdating COVID-19 diagnoses to the date of admission once they received one- or two-day delayed PCR results, we would detect significant backdating through comparison of serially posted databases. During the past 10 days, we estimate that such backdating accounted for less than 4 percent of all admissions.