Surveillance of RSV

What to know

  • CDC maintains surveillance systems to monitor respiratory diseases, including RSV, across the United States.
  • RSV season begins in the fall, peaks in the winter, and ends in the spring in most of the United States.

Surveillance and research systems

CDC has several systems that focus on monitoring and describing seasonal trends, clinical risk factors, rates of illness and hospitalization, and demographics of patients seeking care for illness associated with respiratory syncytial virus (RSV).

RSV burden estimates

Each year in the United States, RSV leads to approximately:

  • 2.1 million outpatient (non-hospitalization) visits among children younger than 5 years old.(1)
  • 58,000-80,000 hospitalizations among children younger than 5 years old.(1,2,3)
  • 60,000-160,000 hospitalizations among adults 65 years and older.(4-8)
  • 6,000-10,000 deaths among adults 65 years and older.(9-11)
  • 100–300 deaths in children younger than 5 years old.(11)

RSV seasonal trends

How are data collected?

CDC collects RSV laboratory test results performed in the United States using a surveillance system called the National Respiratory and Enteric Virus Surveillance System (NREVSS). CDC analyzes data on RSV activity at the national, regional, and state levels. This is a voluntary, laboratory-based surveillance system established in the 1980s to monitor trends in several viruses, including RSV. Through NREVSS, participating laboratories report the total number of weekly RSV tests performed to detect the virus, and the number of those tests that were positive. They also report the method used for detection, and the location and date of specimen collection. Serotyping, demographic data, and clinical data are not reported. Data from NREVSS provides information to public health officials and healthcare providers about the presence of RSV in their communities.

What are the typical seasonal patterns?

In most regions of the United States and other areas with similar climates, RSV season typically starts during the fall and peaks in the winter. Based on data from before the COVID-19 pandemic (2014 to 2017), in all 10 U.S. Department of Health and Human Services (HHS) regions, except Florida and Hawaii these patterns were observed(12):

  • RSV season onset (indicating a sustained rise in the number of RSV-positive tests) ranged from mid-September to mid-November.
  • RSV season peak (indicating the maximum number of RSV-positive tests) ranged from late December to mid-February.
  • RSV season offset (indicating a sustained drop in the number of RSV-positive tests) ranged from mid-April to mid-May.

Florida has an earlier RSV season onset and longer duration than most regions of the country.

Prior to 2020, seasonal patterns for RSV in the United States were very consistent.(12) However, the patterns of circulation for RSV and other common respiratory viruses have been disrupted since the start of the COVID-19 pandemic early in 2020. Beginning in the southern region of the United States, RSV circulation began to rise in the spring months of 2021 and peaked in July.(13) It is too soon to predict when the previous seasonal patterns will return.


  1. Hall CB, Weinberg GA, Iwane MK, et al. The burden of respiratory syncytial virus infection in young children. New Engl J Med. 2009;360(6):588–98.
  2. Rha B, Curns AT, Lively JY, et al. Respiratory Syncytial Virus–Associated Hospitalizations Among Young Children: 2015–2016. Pediatrics. 2020;146(1):e20193611.
  3. McLaughlin JM, Khan F, Schmitt H-J, et al. Respiratory Syncytial Virus–Associated Hospitalization Rates among US Infants: A Systematic Review and Meta-Analysis. J Infect Dis. 2022;225(6):1100-1111.
  4. Widmer K, Zhu Y, Williams JV, et al. Rates of Hospitalizations for Respiratory Syncytial Virus, Human Metapneumovirus, and Influenza Virus in Older Adults. J Infect Dis. 2012; 206(1):56-62.
  5. Branche AR, Saiman L, Walsh EE, et al. Incidence of Respiratory Syncytial Virus Infection Among Hospitalized Adults, 2017–2020. Clin Infect Dis. 2022;74(6):1004-1011.
  6. McLaughlin JM, Khan F, Begier E, et al. Rates of Medically Attended RSV among US Adults: A Systematic Review and Meta-analysis. Open Forum Infect Dis. 2022; 9(7): ofac300.
  7. Zheng Z, Warren JL, Shapiro ED, et al. Estimated incidence of respiratory hospitalizations attributable to RSV infections across age and socioeconomic groups. Pneumonia. 2022;14(1):6.
  8. CDC unpublished data from RSV-NET. Available at:
  9. Thompson WW, Shay DK, Weintraub E, et al. Mortality Associated with Influenza and Respiratory Syncytial Virus in the United States. JAMA. 2003; 289(2): 179.186.
  10. Matias G, Taylor R, Haguinet F, et al. Estimates of mortality attributable to influenza and RSV in the United States during 1997–2009 by influenza type or subtype, age, cause of death, and risk status. Influenza Other Respir Viruses. 2014; 8(5):507-15.
  11. Hansen CL, Chaves SS, Demont C, Viboud C. Mortality Associated With Influenza and Respiratory Syncytial Virus in the US, 1999-2018. JAMA Network Open. 2022 Feb 1;5(2):e220527.
  12. Centers for Disease Control and Prevention. Respiratory Syncytial Virus Seasonality — United States, 2014–2017.MMWR. 2018;67(2):71–76.
  13. Centers for Disease Control and Prevention. Changes in Influenza and Other Respiratory Virus Activity During the COVID-19 Pandemic — United States, 2020–2021.MMWR. 2021;70(29):1013–1019.