Purpose and Methods
Population-based surveillance is the collection, analysis, and interpretation of data on a population in a specified area.
COVID-NET is a population-based surveillance system.
Coronavirus Disease 2019 (COVID-19)-Associated Hospitalization Surveillance Network (COVID-NET) is a population-based surveillance system that collects data on laboratory-confirmed COVID-19-associated hospitalizations among children and adults through a network of over 250 acute-care hospitals in 14 states.
Why COVID-NET Data Is Important
COVID-NET is CDC’s source for important data on hospitalization rates associated with COVID-19. Hospitalization rates are updated weekly. COVID-NET also provides important clinical information on COVID-19-associated hospitalizations, including age group, sex, race/ethnicity and underlying health conditions.
COVID-NET Data Collection, Timeliness and Interpretation
Cases are identified in COVID-NET if they test positive for SARS-COV-2 (the virus that causes COVID-19 disease) through a test ordered by a health care professional and are hospitalized within 14 days of the positive test. Clinical data are collected using a standardized case reporting form by trained surveillance officers, so the data are collected in a standardized and uniform way.
COVID-NET is expected to collect the following data for each case:
- surveillance site
- date of hospital admission
- evidence of positive SARS-CoV-2 test
- demographic information (e.g., race, ethnicity)
- clinical (medical) history (underlying health conditions)
- clinical course (progression of the illness such as admission to an intensive care unit)
- medical interventions (medical care for the illness such as need for mechanical ventilation)
- outcomes (e.g., released from the hospital, death)
How COVID-NET Hospitalization Data Is Different from Hospitalizations Reported in National and State Case Counts
COVID-NET differs from hospitalizations reported in national and state case counts in two ways. First, state and national COVID-19 case reporting are based on all people who test positive for COVID-19 in the United States. COVID-NET is limited to COVID-19-associated hospitalizations captured in the COVID-NET surveillance area. Second, COVID-NET reports rates and not just counts. These rates show how many people are hospitalized with COVID-19 in the surveillance area, compared to the entire number of people residing in that area.
How COVID-NET Calculates Hospitalization Rates
Hospitalization rates are calculated by the number of residents of a defined area who are hospitalized with a positive SARS-CoV-2 laboratory test divided by the total population within that defined area.
COVID-NET comprises 99 counties in the 14 states participating in the Emerging Infections Program (EIP) and the Influenza Hospitalization Surveillance Project (IHSP). Participating states include: California, Colorado, Connecticut, Georgia, Iowa, Maryland, Michigan, Minnesota, New Mexico, New York, Ohio, Oregon, Tennessee, and Utah.
COVID-NET covers approximately 10 percent of the U.S. population. The counties covered are located in all 10 Health and Human Services (HHS) regionsexternal icon. The designated COVID-NET surveillance area is generally similar to the U.S. population by demographics; however, the information might not be generalizable to the entire country.
Accessing COVID-NET Data
COVID-19-associated hospitalization rates are reported to CDC on a weekly basis. COVID-NET data, including hospitalization rates for different age groups and data on patient characteristics, are available on COVIDView
COVID-NET hospitalization data are preliminary and may change as more data is received. In particular, case counts and rates for recent hospital admissions are subject to lag. As data are received each week, prior case counts and rates are updated accordingly.
- Owusu D, Kim L, O’Halloran A, et al. Characteristics of Adults aged 18-49 years without Underlying Medical Conditions Hospitalized with Laboratory Confirmed COVID-19 in the United States, COVID-NET – March – August 2020.external icon Clin Infect Dis. Published online December 3, 2020.
- Acosta AM, Mathis AL, Budnitz DS, et. Al. COVID-19 investigational treatments in use among hospitalized patients identified through the U.S. Coronavirus Disease 2019 -Associated Hospitalization Surveillance Network, March 1–June 30, 2020.external icon Open Forum Infectious Disease. Published on-line November 9, 2020.
- Kambhampati AK, O’Halloran AC, Whitaker M, et al. COVID-19–Associated Hospitalizations Among Health Care Personnel — COVID-NET, 13 States, March 1–May 31, 2020. MMWR Morb Mortal Wkly Rep 2020;69:1576–1583.
- Ko JY, Danielson ML, Town M, et al. Risk Factors for COVID-19-associated hospitalization: COVID-19-Associated Hospitalization Surveillance Network and Behavioral Risk Factor Surveillance System.external icon Clin Infect Dis. Published online September 18, 2020.
- Delahoy MJ, Whitaker M, O’Halloran, et. al. Characteristics and Maternal and Birth Outcomes of Hospitalized Pregnant Women with Laboratory-Confirmed COVID-19 — COVID-NET, 13 States, March 1–August 22, 2020. MMWR Morb Mortal Wkly Rep. 2020;69:1347–1354.
- Kim L, Whitaker M, O’Halloran A, et al. Hospitalization Rates and Characteristics of Children Aged <18 Years Hospitalized with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, March 1–July 25, 2020.e