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Coronavirus Disease 2019 (COVID-19)-Associated Hospitalization Surveillance Network (COVID-NET)
A RESP-NET Platform
About COVID-NET
The Coronavirus Disease 2019 (COVID-19) Hospitalization Surveillance Network (COVID-NET) is designed to conduct population-based surveillance for laboratory-confirmed COVID-19-associated hospitalizations among children and adults.
COVID-NET, along with the Respiratory Syncytial Virus Hospitalization Surveillance Network (RSV-NET) and the Influenza Hospitalization Surveillance Network (FluSurv-NET), comprise the Respiratory Virus Hospitalization Surveillance Network (RESP-NET). The RESP-NET platforms have overlapping surveillance areas and use similar methods to collect data.
COVID-NET is CDC’s source for important data on rates of hospitalizations associated with COVID-19. Hospitalization rates show how many people in the surveillance area are hospitalized with COVID-19, compared to the total number of people residing in that area.
Why COVID-NET Data Are Important
Tracking COVID-19-associated hospitalization rates helps public health professionals understand trends in virus circulation, estimate disease burden, and respond to outbreaks. Hospitalization rates are updated weekly on COVID-NET interactive. Collecting demographic and more detailed clinical information, including underlying conditions, allows CDC to better understand COVID-19-associated hospitalization trends and determine who is most at risk.
Case Definition
A case is defined by laboratory confirmed SARS-CoV-2 in a person who:
- Lives in a defined COVID-NET surveillance area AND
- Tests positive for SARS-CoV-2 within 14 days before or during hospitalization.
Evidence of COVID-19 infection can be obtained through several laboratory tests:
- Molecular assays, such as reverse transcription polymerase chain reaction (RT-PCR)
- Commercially available rapid antigen detection tests
- Serology (antibody) tests (must be paired acute and convalescent specimens)
Calculating Hospitalization Rates
To calculate COVID-19-associated hospitalization rates, COVID-NET collects the following data from identified cases:
- Age
- Sex
- Race and ethnicity
- County of residence
- Date of hospital admission
- Date of SARS-CoV-2 test
- Positive SARS-CoV-2 test result
Hospitalization rates are calculated as the number of residents in a surveillance area who are hospitalized with laboratory-confirmed COVID-19, divided by the total population estimate for that area. NCHS bridged-race population estimates are used as denominators for rate calculations.
How COVID-NET Hospitalization Data Are Different from Hospitalizations Reported in National and State Case Counts
COVID-NET data differ from hospitalizations reported in national and state case counts in multiple ways. First, state and national COVID-19 case reporting is based on all people who test positive using a healthcare provider-administered test 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, not just counts. These rates show how many people are hospitalized with COVID-19 in the surveillance area, compared to the population residing in that area.
Collecting Clinical Data
COVID-NET surveillance began tracking COVID-19-associated hospitalizations in adults in March of 2020.
Cases are identified by reviewing state surveillance system databases, health information exchanges, hospital admission and laboratory databases, and infection control logs for patients hospitalized with a positive SARS-CoV-2 test result. Data collected are used to estimate age-specific hospitalization rates on a weekly and monthly basis and describe demographic and clinical characteristics of patients hospitalized with COVID-19.
Trained surveillance officers collect clinical data using a standardized case reporting form. Clinical data collected include:
- Medical history (e.g., underlying health conditions)
- Clinical course (i.e., progression of the COVID-19 illness such as admission to an ICU)
- Medical interventions (i.e., medical care for the COVID-19 illness such as need for mechanical ventilation)
- Outcomes (i.e., discharged from the hospital, or death)
- COVID-19 vaccination history
COVID-NET Surveillance Area
COVID-NET currently comprises 98 counties in the 13 states participating in the Emerging Infections Program (EIP) and the Influenza Hospitalization Surveillance Project (IHSP). The participating states are California, Colorado, Connecticut, Georgia, 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 nine of the 10 Health and Human Services (HHS) regionsExternal. The designated COVID-NET surveillance area is generally similar to the U.S. population by demographics; however, the statistics generated using COVID-NET data 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, data on patient characteristics, and hospitalization rates by vaccination status are available on the CDC COVID Data Tracker.
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.
COVID-NET Publications
- Ko JY, Pham H, Anglin O, et al. Vaccination Status and Trends in Adult COVID-19-Associated Hospitalizations by Race and Ethnicity, March 2020—August 2022External. Clin Infect Dis. 2023 May 3:ciad266. doi: 10.1093/cid/ciad266. Epub ahead of print.
- Shah MM, Patel K, Milucky J, et al. Bacterial and viral infections among adults hospitalized with COVID-19, COVID-NET, 14 states, March 2020–April 2022External. Influenza Other Respi Viruses. 2023 Mar 2;17(3):e13107. doi: 10.1111/irv.13107
- Woodruff RC, Garg S, George MG, et al. Acute Cardiac Events During COVID-19-Associated HospitalizationsExternal. Journal of the American College of Cardiology. 2023 Feb 14;557–569.
- Agathis NT, Patel K, Milucky J, et al. Codetections of Other Respiratory Viruses Among Children Hospitalized With COVID-19External. Pediatrics. 2023 Feb;151 (2): e2022059037. 10.1542/peds.2022-059037
- O’Halloran A, Whitaker M, Patel K, et al. Developing a sampling methodology for timely reporting of population-based COVID-19-associated hospitalization surveillance in the United States, COVID-NET 2020–2021External. Influenza Other Respi Viruses. 2023 Jan 10; 1-8.
- Adams K, Tastad KJ, Huang S, et al. Prevalence of SARS-CoV-2 and Influenza Coinfection and Clinical Characteristics Among Children and Adolescents Aged <18 Years Who Were Hospitalized or Died with Influenza — United States, 2021–22 Influenza SeasonExternal. MMWR Morb Mortal Wkly Rep. 2022 Dec 16;71(50):1589–1596.
- Hamid S, Woodworth K, Pham H, et al. COVID-19–Associated Hospitalizations Among U.S. Infants Aged <6 Months — COVID-NET, 13 States, June 2021–August 2022External. MMWR Morb Mortal Wkly Rep. 2022 Nov 11;71(45):1442–1448.
- Havers FP, Pham H, Taylor CA, et al. COVID-19-Associated Hospitalizations Among Vaccinated and Unvaccinated Adults 18 Years or Older in 13 US States, January 2021 to April 2022 | Critical Care Medicine | JAMA Internal Medicine | JAMA NetworkExternal JAMA Intern Med. 2022 Oct 1;182(10):1071–1081.
- Havers FP, Patel K, Whitaker M, et al. Laboratory-Confirmed COVID-19–Associated Hospitalizations Among Adults During SARS-CoV-2 Omicron BA.2 Variant Predominance — COVID-19–Associated Hospitalization Surveillance Network, 14 States, June 20, 2021–May 31, 2022External. MMWR Morb Mortal Wkly Rep. 2022 Aug 26;71:1085–1091.
- Sekkarie A; Woodruff R, Whitaker M et al. Characteristics and treatment of hospitalized pregnant women with COVID-19. American Journal of Obstetrics & Gynecology MFMExternal. Am J Obstet Gynecol MFM. 2022 Aug 12;4(6):100715.
- Singson JRC, Kirley PD, Pham H, et al. COVID-NET Surveillance Team, Reingold A, Chai SJ. Factors Associated with Severe Outcomes Among Immunocompromised Adults Hospitalized for COVID-19 – COVID-NET, 10 States, March 2020-February 2022External. MMWR Morb Mortal Wkly Rep. 2022 Jul 8;71(27):878-884.
- Steele MK, Couture A, Reed C, et al. Estimated Number of COVID-19 Infections, Hospitalizations, and Deaths Prevented Among Vaccinated Persons in the US, December 2020 to September 2021External. JAMA Netw Open. 2022 Jul 1;5(7):e2220385.
- Delahoy MJ, Ujamaa D, Taylor CA, et al. Comparison of influenza and COVID-19-associated hospitalizations among children < 18 years old in the United States-FluSurv-NET (October-April 2017-2021) and COVID-NET (October 2020-September 2021)External. Clin Infect Dis. 2022 May 20:ciac388.
- Couture A, Iuliano D, Chang H, et al. Estimating COVID-19 Hospitalizations in the United States with Surveillance Data Using a Bayesian Hierarchical Model: A Modeling StudyExternal. JMIR Public Health Surveill. 2022 Jun 2;8(6):e34296.
- Shi DS, Whitaker M, Marks KJ, et al. Hospitalizations of Children Aged 5-11 with Laboratory-Confirmed COVID-19 ― COVID-NET, 14 States, March 2020-February 2022.External MMWR Morb Mortal Wkly Rep. 2022 Apr 22;71(16):574-581
- Taylor CA, Whitaker M, Anglin O, et al. COVID-19–Associated Hospitalizations Among Adults During SARS-CoV-2 Delta and Omicron Variant Predominance, by Race/Ethnicity and Vaccination Status — COVID-NET, 14 States, July 2021–January 2022. MMWR Morb Mortal Wkly Rep. 2022 Mar 25; 71(12):466-473.
- Marks KJ, Whitaker M, Agathis NT, et al. Hospitalization of Infants and Children Aged 0–4 Years with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, March 2020–February 2022External. MMWR Morb Mortal Wkly Rep. 2022 Mar 18;71(11):429–436.
- Marks KJ, Whitaker M, Agathis NT, et al. Hospitalization of Infants and Children Aged 0–4 Years with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, March 2020–February 2022External. MMWR Morb Mortal Wkly Rep. 2022 Mar 18;71(11):429–436.
- Woodruff RC, Campbell AP, Taylor CA, et al. Risk factors for severe COVID-19 in childrenExternal. Pediatrics. 2022 Jan 1;149(1):e2021053418.
- Taylor CA, Patel K, Pham H, et al. Severity of Disease Among Adults Hospitalized with Laboratory-Confirmed COVID-19 Before and During the Period of SARS-CoV-2 B.1.617.2 (Delta) Predominance — COVID-NET, 14 States, January–August 2021External. MMWR Morb Mortal Wkly Rep. 2021 Oct 29;70(43):1513–1519.
- Acosta AM, Garg S, Pham H, et al. Racial and Ethnic Disparities in Rates of COVID-19–Associated Hospitalization, Intensive Care Unit Admission, and In-Hospital Death in the United States From March 2020 to February 2021External. JAMA Netw Open.2021 Oct 1;4(10):e2130479.
- Wortham JM, Meador SA, Hadler JL, et al. Census tract socioeconomic indicators and COVID-19-associated hospitalization rates-COVID-NET surveillance areas in 14 states, March 1-April 30, 2020External. PLoS One. 2021 Sep 24;16(9):e0257622.
- Delahoy MJ, Ujamaa D, Whitaker M, et al. Hospitalizations Associated with COVID-19 Among Children and Adolescents — COVID-NET, 14 States, March 1, 2020–August 14, 2021External. MMWR Morb Mortal Wkly Rep. 2021 Sep 10;70(36):1255–1260.
- Havers, F. P., Pham, H., Taylor, C. A, et al. COVID-19-associated hospitalizations among vaccinated and unvaccinated adults ≥18 years – COVID-NET, 13 states, January 1 – July 24, 2021External. 2021 Aug 29.
- Moline HL, Whitaker M, Deng L, et al. Effectiveness of COVID-19 Vaccines in Preventing Hospitalization Among Adults Aged ≥65 Years — COVID-NET, 13 States, February–April 2021External. MMWR Morb Mortal Wkly Rep. 2021 Aug 13;70(32):1088-1093.
- Garg S, Patel K, Pham H, et al. Clinical Trends Among U.S. Adults Hospitalized With COVID-19, March to December 2020: A Cross-Sectional StudyExternal. Ann Intern Med. 2021 Oct; 174(10):1409-1419.
- Havers FP, Whitaker M, Self JL, et al. Hospitalization of Adolescents Aged 12–17 Years with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, March 1, 2020–April 24, 2021External. MMWR Morb Mortal Wkly Rep. 2021 Jun 11;70(23):851–857.
- 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.ExternalClin Infect Dis. 2021 Jun 1;72 (11):e695-e703.
- Cha S, Henry A, Montgomery MP, et al. Morbidity and Mortality among Adults Experiencing Homelessness Hospitalized with COVID-19External. J Infect Dis. 2021 Aug 2;224(3):425-430.
- Kim L, Garg S, O’Halloran A, et al. Risk Factors for Intensive Care Unit Admission and In-hospital Mortality among Hospitalized Adults Identified through the U.S. Coronavirus Disease 2019 (COVID-19)-Associated Hospitalization Surveillance Network (COVID-NET).ExternalClin Infect Dis. 2021 May 4;72(9): e26-e214.
- 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 2020External. Clin Infect Dis. 2021 Mar 1;72(5): e162-166.
- Joo H, Miller GF, Sunshine G, et al. Decline in COVID-19 Hospitalization Growth Rates Associated with Statewide Mask Mandates — 10 States, March–October 2020External. MMWR Morb Mortal Wkly Rep. 2021 Feb 26;70(8):212–216.
- 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 Open Forum Infectious Disease. 2020 Nov 9;5(11): ofaa528.
- 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, 2020External. MMWR Morb Mortal Wkly Rep. 2020 Nov 13;69(45):1576–1583.
- 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, 2020External. MMWR Morb Mortal Wkly Rep. 2020 Sep 25;69(38):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.ExternalMMWR Morb Mortal Wkly Rep. 2020 Aug 14;69(32):1081–1088.
- 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.External MMWR Morb Mortal Wkly Rep. 2020 Apr 17;69(15):458-464.