Who Was Hospitalized with COVID-19 in March 2020: The First Month of COVID-NET

A report from the first month of the pandemic's U.S. surveillance, posted as an MMWR Early Release on April 8, 2020.

Hospitalization rates per 100,000 by age group, March 2020, with CDC's advice at the time. Graphic: CDC.

Summary

• Known before: population-based rates of laboratory-confirmed COVID-19 hospitalizations in the United States were lacking.
• New here: COVID-NET was set up to produce reliable weekly, age-stratified hospitalization rates. Rates rise with age and are highest in older adults, and most hospitalized patients have underlying conditions.
• What it means: prevention — social distancing, respiratory hygiene, and face coverings in public where distancing is hard — matters most for protecting older adults and people with underlying conditions. Continued monitoring is needed to follow the epidemic and plan health care resources.

The network

By early April 2020, about 1.3 million COVID-19 cases had been reported worldwide, about 330,000 of them in the United States. To track hospitalizations, CDC built the COVID-19–Associated Hospitalization Surveillance Network (COVID-NET) on the existing networks for influenza (FluSurv-NET) and RSV (RSV-NET).

• It covers 99 counties in 14 states — California, Colorado, Connecticut, Georgia, Iowa, Maryland, Michigan, Minnesota, New Mexico, New York, Ohio, Oregon, Tennessee and Utah — across all 10 Department of Health and Human Services regions, about 10% of the U.S. population.
• A case is a resident of the area hospitalized within 14 days of a positive SARS-CoV-2 test (any test with Emergency Use Authorization); testing was at clinicians' discretion.
• Surveillance officers find cases in disease, laboratory and hospital records, then abstract medical charts for patient characteristics, underlying conditions, clinical course and outcomes.
• Surveillance began on March 23, 2020, looking back to March 1. Rates are shown through March 28 (week 13) and clinical data through March 30. Weekly rates have been published online since April 3.

Hospitalization rates

For the four weeks ending March 28, 2020, the rate was 4.6 per 100,000 population.

Laboratory-confirmed COVID-19 hospitalization rates by age group, 14 states, March 1–28, 2020. Chart: CDC.

Rates varied widely by surveillance site.

Hospitalization rates by surveillance site, March 1–28, 2020. Chart: CDC.

Who was hospitalized

Of 1,482 patients:

• 74.5% were 50 or older: 643 (43.4%) were 65 or older, 461 (31.1%) were 50–64, 366 (24.7%) were 18–49, and six each were 0–4 and 5–17.
• 805 (54.4%) were men; the rate was higher in males (5.1 per 100,000) than females (4.1).
• Among 580 with race and ethnicity recorded, 45.0% were white, 33.1% Black, 8.1% Hispanic, 5.5% Asian, 0.3% American Indian or Alaska Native, and 7.9% other or unknown.

In the network's population, about 49% of residents are male, 59% white, 18% Black and 14% Hispanic — so men and Black people may be disproportionately affected, findings that need confirming with more data.

Underlying conditions and symptoms

Detailed data were available for about 180 adults (12%). 89.3% had at least one underlying condition.

• By age: in adults 18–49, obesity was most common, then chronic lung disease (mainly asthma) and diabetes; at 50–64, obesity, then hypertension and diabetes; at 65 and older, hypertension, then cardiovascular disease and diabetes.
• Pregnancy: 3 of 33 (9.1%) women aged 15–49 were pregnant — similar to the estimated 9.9% of women aged 15–44 who are pregnant at any given time (2010 data).
• Timing: among 167 patients, the median time from symptom onset to admission was 7 days (interquartile range 3–9).
• Symptoms at admission: cough (86.1%), fever or chills (85.0%) and shortness of breath (80.0%) were most common; diarrhea (26.7%) and nausea or vomiting (24.4%) were also frequent.

How it compares

• In the first four weeks, rates ran from 0.1 per 100,000 (ages 5–17) to 17.2 (85 and older). In the first four weeks of each of the past five flu seasons, cumulative influenza rates ranged from 0.1 (5–17) to 2.2–5.4 (85 and older). These early COVID-19 rates were preliminary and expected to rise as more cases were found and testing expanded.
• Several conditions common in COVID-19 patients are common in the population: in national survey data, hypertension affects 29% of U.S. adults (7.5%–63% by age), and age-adjusted obesity 42%. Among COVID-19 patients, hypertension was 50% and obesity 48%.
• In hospitalized influenza patients in 2014–15 through 2018–19, 41%–51% had cardiovascular disease, 39%–45% chronic metabolic disease, 33%–40% obesity and 29%–31% chronic lung disease — similar to several COVID-19 figures.

Limitations

1. Rates by age and site were preliminary and could change as more cases were identified.
2. Detailed clinical data lag because charts must be reviewed; about 200 had been abstracted by March 30, and many patients were still in hospital.
3. Testing was at clinicians' discretion and varied, so cases were likely undercounted.

Conclusion

Early COVID-NET data showed COVID-19 hospitalizations highest in older adults, with nearly 90% of patients having underlying conditions. Older adults and people with serious underlying conditions should avoid contact with people who are ill and contact their health care provider promptly if they develop symptoms of COVID-19.

Sources

Based on Garg S, Kim L, Whitaker M, et al., "Hospitalization Rates and Characteristics of Patients Hospitalized with Laboratory-Confirmed Coronavirus Disease 2019 — COVID-NET, 14 States, March 1–30, 2020," MMWR Morbidity and Mortality Weekly Report, volume 69, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report gives the number of adults with detailed data both as 178 and as about 180; percentages are as published. Its site chart, whose link was broken in the imported copy, is restored here.