Respiratory Syncytial Virus (RSV) Hospitalization Surveillance Network (RSV-NET)

Respiratory Syncytial Virus (RSV) Hospitalization Surveillance Network (RSV-NET) collects data on severe RSV hospitalizations, including those resulting in ICU admission or death, among children and adults. A network of sites collects and reports data from acute-care hospitals across 75 counties in 12 states from October 1–April 30 each year. In adults, RSV hospitalization tracking began in the 2016–2017 season. In children less than 18 years of age, surveillance began in the 2018–19 season.

RSV-NET uses similar methods to COVID-NET and FluSurv-NET, which are surveillance networks for hospitalizations associated with COVID-19 and influenza, respectively.

Why Are RSV-NET Data Important?

RSV-NET is a population-based surveillance system.

Population-based surveillance is the collection, analysis, and interpretation of data on a population in a specified area.

RSV-NET is an important CDC source of data on hospitalization rates associated with RSV. Tracking RSV hospitalizations helps public health professionals understand virus circulation and disease burden, and respond to outbreaks. In RSV-NET, hospitalization rates are updated monthly. RSV-NET also tracks important demographic information such as age, sex, and race/ethnicity. Additional clinical information such as underlying health conditions are collected for patients with serious hospitalizations, including those who are admitted to the ICU or who die in the hospital.

RSV-NET is limited to RSV-associated hospitalzations captured in the RSV-NET surveillance area, which enables RSV-NET to report rates and not just counts. These rates show how many people are hospitalized with RSV-NET in the surveillance area, compared to the entire number of people residing in that area.

RSV-NET Case Definition

A case is defined as a person who:

  • Is a resident in a defined RSV-NET catchment area and
  • Tests positive for RSV through a test ordered by a healthcare professional within 14 days prior to or during hospitalization.

Evidence of RSV can be obtained through a variety of tests:

  • Molecular assays such as reverse transcription polymerase chain reaction (RT-PCR)
  • Commercially available rapid antigen detection tests
  • Serology (must be paired acute and convalescent specimens)
  • Viral culture
  • Immunofluorescence antibody staining, including direct (DFA) and indirect (IFA) fluorescent antibody test

How RSV-NET Calculates Hospitalization Rates

A minimum set of data are collected on all identified cases to produce hospitalization rates:

  • Age
  • Sex
  • Race and ethnicity
  • Date of hospital admission
  • Positive RSV test result/date

Hospitalization rates are calculated as the number of residents of a defined area who are hospitalized with a positive RSV laboratory test divided by the total population within the defined area. NCHS bridged-race population estimates are used as denominators.

RSV-NET Collection of Clinical Data

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 on all cases who are admitted to the ICU or who die in the hospital. Starting in the 2021–2022 season, clinical data are also collected on all RSV-NET patients who are pregnant. The following clinical data is collected:

  • 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., discharged from the hospital, death)

RSV-NET Coverage

RSV-NET comprises 75 counties in 12 states participating in the Emerging Infections Program (EIP) and the Influenza Hospitalization Surveillance Project (IHSP). Participating states include California, Colorado, Connecticut, Georgia, Maryland, Michigan, Minnesota, New Mexico, New York, Oregon, Tennessee, and Utah.

RSV-NET covers approximately 8.7% percent of the U.S. population. The designated RSV-NET surveillance area is generally similar to the U.S. population by demographics; however, the information might not be generalizable to the entire country.