In the US, there is a lack of data regarding hospitalization rates and characteristics of individuals hospitalized with laboratory-confirmed COVID-19. In newly published findings by the Centers of Disease Control and Prevention (CDC) in the Morbidity and Mortality Weekly Report (MMWR), researchers used the COVID-19–Associated Hospitalization Surveillance Network (COVID-NET) and studied weekly, age-stratified COVID-19 hospitalization rates to discover that the latter increased with age and were highest among older adults. Also, patients with underlying conditions were most likely to be hospitalized.
This information implies that measures to prevent COVID-19, such as respiratory hygiene, social distancing, and face covering in public places are of particular importance to older adults with underlying health complications. Moreover, monitoring hospitalization rates is vital for understanding the progressing epidemiology of the pandemic, and will play a critical role in the organization and prioritization of health care resources.
COVID-NET: What is It and How Does It Operate?
Since the detection of SARS-CoV-2, the novel coronavirus behind the ongoing COVID-19 pandemic, in December 2019, over 1.5 million cases have been confirmed around the world, with over 450,000 reported in the US alone. In order to surveillance population-based hospitalization rates for laboratory-confirmed cases of COVID-19 in the US, the COVID-19–Associated Hospitalization Surveillance Network (COVID-NET) was created. It uses the infrastructure of already existing Influenza Hospitalization Surveillance Network (FluSurv-NET) and the Respiratory Syncytial Virus Hospitalization Surveillance Network (RSV-NET).
COVID-NET monitors population-based hospitalization rates for laboratory-confirmed cases of COVID-19 among people of all ages. It uses data from 99 counties in 14 US states (California, Colorado, Connecticut, Georgia, Iowa, Maryland, Michigan, Minnesota, New Mexico, New York, Ohio, Oregon, Tennessee, and Utah) spread across all 10 regions of the US Department of Health and Human Services. The catchment area (areas from which hospital’s patients are studied) covers about 10% of the US population. COVID-NET surveillance was initiated on March 23, 2020, with the identification of retrospective cases admitted during March 1 to 22, 2020, and prospective case identification during March 23 to 30, 2020. From April 3, 2020, COVID-NET hospitalization rates are being reported every week.
For every case, trained surveillance personnel use a standard case report to collect information regarding patient characteristics, underlying medical conditions, clinical progress and outcomes. Surveillance offers regularly reviewed reportable disease and laboratory databases, hospital admissions and infection control practitioner logs. Chart reviews are finalized after the patient has been discharged. To fulfill the surveillance case definition, a patient must be a resident of a COVID-NET catchment area, and must have been hospitalized within 14 days of receiving a positive COVID-19 test. A laboratory-confirmed SARS-CoV-2 case is defined as a positive result by any test with an Emergency Use Authorization (EUA) for SARS-CoV-2 testing.
This report showed age-stratified hospitalization rates for COVID-19 patients admitted during March 1 to 28, 2020, and presented clinical data on patients admitted during March 1 to 30, 2020. Out of the 1,482 patients hospitalized, 74.5% were over 50 years of age, and 54.4% were male. The hospitalization rate during this period was 4.6 per 100,000 population, with the highest rates (13.8) reported for adults older than 65. During the first month of surveillance, COVID-NET hospitalization rates ranged from 0.1 per 100,000 population in patients aged 5 to 17 years, to 17.2 per 100,000 population in adults more than 85 years old.
Among the 178 (12%) adult patients with underlying condition, 89.3% reported having more than one health complication, the most common being as follows: hypertension (49.7%), diabetes mellitus (28.3%), obesity (48.3%), cardiovascular disease (27.8%) and chronic lung disease (34.6%).
Limitations and Implications of the Report
Researchers have mentioned at least four limitations in the report. First, the rates mentioned are preliminary and should be interpreted with caution due to the continuously evolving nature of SARS-CoV-2, since hospitalization rates as well as the frequency and distribution of underlying conditions are expected to increase as the pandemic progresses and additional cases are reported. Second, availability of detailed clinical data was delayed because of the need for medical chart abstractions. Third, testing for SARS-CoV-2 through COVID-NET is conducted at the discretion of treating health care providers and testing procedures, and expertise may vary significantly across providers and facilities. As a consequence, under- ascertainment of cases in COVID-NET is possible. Lastly, inferences made from the catchment population might suggest males to be disproportionately affected by COVID-19 as compared to females. Similarly, black populations might be disproportionately represented and shown to be more affected by COVID-19.
Nevertheless, significant conclusions may be drawn from the report. Early data critically suggests that COVID-19–associated hospitalizations in the US are highest for older adults, and nearly 90% of all hospitalized patients have one or more underlying medical conditions. The findings highlight the importance of strictly implementing preventive measures – social distancing, personal hygiene, face covering in public settings – especially for older adults. Ongoing monitoring of hospitalization rates, clinical progress and outcomes of patients will play a significant role in understanding the epidemiology and clinical spectrum of COVID-19 in the US, ultimately guiding health care resources to devise better strategies.