Respiratory Syncytial Virus (RSV) Associated Hospitalizations Surveillance (RSV-NET)

Overview

RSV is a major cause of respiratory infection and hospital visits in the United States, affecting extremes of age. As of May 2023, two vaccines have been approved for use in adults over the age of 60 and one of those vaccines has since been approved for use in pregnant women as well. In July 2023, the FDA approved the use of the monoclonal antibody Beyfortus for the prevention of RSV in infants up to 2 years of age.

The Respiratory Syncytial Virus Hospitalization Surveillance Network (RSV-NET) is a population-based surveillance system that collects data on laboratory-confirmed RSV-associated hospitalizations among children and adults through a network of acute-care hospitals in 12 states participating in the Emerging Infections Program (EIP) and is part of the Respiratory Virus Hospitalization Surveillance Network (RESP-NET). The purpose is to inform clinical and public health response and to estimate the national disease burden of RSV.

Objectives

Primary

  1. Estimate overall and age-specific RSV hospitalization rates during the respiratory season (October 1st through April 30th) for RSV cases of all ages.
  2. Estimate overall and age-specific RSV-associated mortality rates during the respiratory season (October 1st through April 30th) for RSV cases of all ages that were hospitalized. 
  3. To better understand the most severe cases of RSV disease (e.g., ICU and deaths, etc.) by describing patient characteristics and clinical course.

Secondary

  1. Describe characteristics of all cases hospitalized with laboratory-confirmed RSV that were not hospitalized in the ICU or deceased.
  2. Assess risk factors for RSV-associated complications among hospitalized cases.

Active Surveillance

CEIP Surveillance Officers complete a standardized case report form (CRF) for a subset of cases hospitalized in the previous month, following CDC’s sampling guidance, to inform clinical and public health response. Information collected for each sampled case includes demographics, admission and discharge information and clinical course.

Case Definition

For the purpose of this surveillance project, a case-patient is defined as:

  • A resident of Alameda, Contra Costa or San Francisco counties
  • Admitted to the hospital no more than 14 days after a positive RSV test

Evidence of RSV infection can be obtained through several laboratory tests:

  • Viral culture,
  • Immunofluorescence antibody staining (Direct [DFA] or indirect [IFA])
  • Molecular assay
  • commercially available rapid antigen diagnostic test

Burden Estimation

The purpose of the Burden Estimation Project is to assess under-ascertainment of persons hospitalized with influenza, RSV, and COVID-19 from non-testing and under-reporting in order to adjust the number of confirmed cases reported in RESP-NET. These efforts will contribute to the seasonal multiplier model used to estimate the annual disease burden of influenza, COVID-19, and RSV cases, hospitalizations, and deaths. There are two primary objectives of the project:

  1. To determine the frequency of influenza, RSV, and SARS-CoV-2 testing and test types used to estimate multipliers to correct for the under-detection of influenza, RSV, and COVID-19-associated hospitalizations.
  • To use multipliers to determine the annual burden of influenza-, RSV-, and COVID-19-associated hospitalizations and the burden averted through vaccination and other clinical interventions.

Death Ascertainment

Surveillance data are linked to state vital death data to determine whether a case-patient has died during hospitalization or within 60 days after discharge date.

Geocoding and Linkage to Census Data

Case address at time of admission is geocoded for a sample of cases using standard software to determine the census tract of residence. The census tract is linked to US Census data to obtain socioeconomic indicators associated with the census tract. These data can be used to find associations between geographic location, socioeconomic indicators, and risk for hospitalization with RSV.

Publications

Publications containing important public health findings derived from the surveillance data collected by the CEIP and the national RESP-Net sites can be found at the following link

https://www.cdc.gov/rsv/references.html

Contact

For questions about Influenza surveillance and projects, please contact:

Pam Daily Kirley, MPH
California Emerging Infections Program
RESP-NET Project Manager
respnet@ceip.us

Information and Guidance for the Public: