Respiratory syncytial virus (RSV)


RSV summary1-3

Pathogenic agent

Respiratory syncytial virus (RSV)




Coughs and sneezes from infected persons; hand contact on hard or soft surfaces; follows seasonal pattern of annual epidemics, peaking in winter months


  • Nearly all children are infected with RSV at least once within the first 2 years of life
  • Because many infected individuals are asymptomatic or have mild disease and do not visit health services, quantifying the total burden of disease is challenging
  • RSV is a leading cause of lower respiratory tract infection (LRTI) in infants and young children, and significantly impacts older people aged 60+ years
  • RSV-associated LRTI estimated to account for between 94,600 and 149,400 deaths annually
  • Globally, 33 million RSV-associated LRTIs result in over 3 million hospital admissions annually
  • RSV-related hospitalization costs US healthcare systems $150–680 million annually

Respiratory syncytial virus (RSV) can cause severe lower respiratory tract illness (LRTI), especially inflammation of small airways in the lung, in adults of all ages and bronchiolitis in infants and children.1 RSV is a leading cause of LRTIs and the leading viral cause of severe lower respiratory tract disease in infants and young children around the world.2 RSV infection also significantly impacts people aged 65 years or older, a population that is also vulnerable to seasonal influenza.3-6

Each year, RSV causes over 33 million cases of acute LRTI globally, 3.2 million hospitalizations, and approximately 118,000 deaths in children under the age of 5 years.2

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Up to 10% of hospitalized infants with RSV infection require admission to an intensive care unit (ICU), and death rates can be substantially increased when the child has an ongoing (chronic) health condition.1

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Death rates following RSV infection may be even higher among the elderly than in children—RSV is thought to cause about 14,000 deaths per year among Americans aged over 65 years.5 RSV infections also have a significant economic cost: in the US alone, the cost to the healthcare system is estimated to be $150–680 million every year.5

What characterizes RSV?

Nearly all children are infected with RSV at least once within the first 2 years of life.1 The virus circulates in two major subtypes—A and B—and there are often several strains of these subtypes in circulation at the same time.1 Like influenza, RSV is associated with annual outbreaks or epidemics following a seasonal pattern, peaking in the winter months.1 Children are often infected with RSV every year but tend to experience progressively reduced symptoms as their immune system learns to recognize and fight the virus.1 Older children and adults, therefore, usually don’t experience any symptoms, despite being frequently infected.1

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Management of severe RSV-related bronchiolitis (requiring hospitalization) is largely through supportive care, such as intravenous fluids and supplemental oxygen.1 Inhaled medicines, such as bronchodilators or corticosteroids, may also have limited effect in improving outcomes.1 Only one prophylactic product, palivizumab (an anti-RSV monoclonal antibody), is approved to help prevent serious LRTI in high-risk infants and young children.1

Need for RSV vaccine development

There are currently no vaccines approved for immunization against RSV in either adults or children.1,7 Because infants are usually exposed to RSV at a very young age, a vaccine would need to be given soon after birth when the immune system is not yet mature.1 Such a vaccine would be difficult to test.1 Different obstacles to RSV vaccine development exist for the elderly, namely, an incomplete understanding of the immune responses needed for protection, the effect of aging on immunity, and the high rate of comorbid diseases.7 Nonetheless, RSV is susceptible to neutralizing antibodies, and a number of new vaccines for the protection of children and the elderly are undergoing clinical development.7-9

  1. Borchers AT, et al. Respiratory syncytial virus—a comprehensive review. Clin Rev Allergy Immunol. 2013;45:331–379.
  2. Verwey C, Nunes M. RSV lower respiratory tract infection and lung health in the first 2 years of life. Lancet Glob Health. 2020;8(10):e1247–1248.
  3. Fasley A, Walsh E. Respiratory syncytial virus infection in elderly adults. Drugs Aging. 2005;22:577–587.
  4. Griffiths C, et al. Respiratory syncytial virus: infection, detection, and new options for prevention and treatment. Clin Microbiol Rev. 2016;30:277–319.
  5. Stephens LM, Varga SM. Considerations for a respiratory syncytial virus vaccine targeting an elderly population. Vaccines. 2021;9:624.
  6. Battles MB, McLellan JS. Respiratory syncytial virus entry and how to block it. Nat Rev Microbiol. 2019;17:233–245.
  7. Green CA, et al. Vaccination against respiratory syncytial virus. Interdiscip Top Gerontol Geriatr. 2020;43:182–192.
  8. Graham BS. Vaccine development for respiratory syncytial virus. Curr Opin Virol. 2017;23:107–112.
  9. Ruckwardt TJ, et al. Immunological lessons from respiratory syncytial virus vaccine development. Immunity. 2019;51:429–442.