RSV—Hospitalization, Seasonality, and Pathophysiology

All infants are at risk for RSV lower respiratory tract disease¹

What is RSV?

RSV is a common, highly contagious respiratory virus, the transmission of which occurs through the nasopharyngeal or conjunctival mucosa with respiratory secretions from infected individuals—mostly other children, older siblings, and other family members.²⁻⁴ We cannot predict which infants will develop RSV lower respiratory tract disease.¹

RSV incidence and hospitalization rate in infants

RSV is the leading cause of hospitalization in infants under 12 months.⁵
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2 out of 3 infants will be infected
with RSV by age 1⁶
Infants younger than 1 icon
Infants younger than 1 year are on average
16x more likely to be hospitalized due to RSV than for influenza⁷*
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Among children hospitalized due to RSV:
~75% were born at full term with no
underlying conditions1,8,9†

Learn about RSV seasonality

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RSV is seasonal, with infections peaking at certain times throughout the year.4,11 A typical RSV season runs roughly from Fall through Spring, with some exceptions, such as in Florida, where the RSV season may start earlier.¹² Epidemiology monitoring can identify research when local RSV seasons begin.

One common misperception is that an infant born before the RSV season is better protected against the virus than one born during it. However, infants born during the season are exposed to the virus for less time than those born before it. As a result, the number of RSV-hospitalized infants born in season vs before the season is roughly equal.13*

RSV pathophysiology—see how RSV symptoms progress*

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At Days 1 and 2

Droplets containing RSV from infected contact enter infant’s nasopharynx. There is usually no manifestation of symptoms at this point.¹⁴

At Days 3 Through 5

Nasopharyngeal cells are sloughed and may be aspirated, carrying RSV to lower respiratory tract cells.¹⁴ Symptoms can include congestion, runny nose, fever, irritability, and poor feeding.

At Days 6 Through 8

RSV-infected epithelial cells can travel deeper into the infant's lungs, infecting the bronchioles and alveoli, causing bronchiolitis and/or pneumonia.¹⁴ Symptoms can include cough, excess phlegm, rapid/difficult breathing, wheezing and/or grunting noises, nasal flaring, and abnormal chest movement when breathing.

Ultimately, 2 to 3 out of every 100 infants with RSV infection may need to be hospitalized. Those who are hospitalized may require supportive care such as oxygen, intubation, and/or mechanical ventilation.¹⁵

Take a deeper dive into RSV


Quality of life burden on United States infants and caregivers due to lower respiratory tract infection and adjusting for selective testing

A pilot prospective observational study estimating the quality of life (QoL) for otherwise healthy term US infants with RSV-LRTI and their caregivers.

Infants admitted to US intensive care units for RSV infection during the 2022 seasonal peak

A surveillance study of 600 infants across 39 hospitals requiring intensive care for RSV infection found that most were delivered full-term and previously healthy.

Optimal site of care for administration of extended half-life respiratory syncytial virus (RSV) antibodies to infants in the United States (US)

A study to assess the time from birth hospitalization discharge to the first outpatient visit among US infants in order to determine optimal site of administration for the extended half-life antibody.

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Power to Help Prevent RSV Disease

Learn how Beyfortus™ (nirsevimab-alip) is the only long-acting antibody designed for RSV disease protection that extends through 5 months¹⁶
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Demonstrated Safety and Efficacy Profile¹⁶

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Want to Know More About Beyfortus?


Beyfortus is indicated for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in:

  • Neonates and infants born during or entering their first RSV season.
  • Children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

Important safety information


Beyfortus is contraindicated in infants and children with a history of serious hypersensitivity reactions, including anaphylaxis, to nirsevimab-alip or to any of the excipients.

Warnings and Precautions

  • Hypersensitivity Including Anaphylaxis: Serious hypersensitivity reactions, including anaphylaxis, have been observed with other human IgG1 monoclonal antibodies. If signs and symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, initiate appropriate medications and/or supportive therapy.
  • Use in Individuals with Clinically Significant Bleeding Disorders: As with other IM injections, Beyfortus should be given with caution to infants and children with thrombocytopenia, any coagulation disorder or to individuals on anticoagulation therapy.

Most common adverse reactions with Beyfortus were rash (0.9%) and injection site reactions (0.3%).

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