Epidemiology

An estimated 2.1 million children younger than 5 years require medical attention annually for an RSV infection.

• it can occur and recur at any age
• by two years of age, nearly all children have been infected by RSV at least once (1)

Out breaks are usually caused by two subtypes, A and B.

• subtype A is usually responsible for more severe disease
• dominant strains shift each year resulting in frequent reinfections (1)

Infection may occur at any time but is least frequent in the summer, accounting for 20 to 25% of hospital admissions for pneumonia of young infants and children and for 75% of cases of bronchiolitis in this age group

• RSV infection is a clearly identified winter virus usually occurring in the UK within the period October to March with most infections occurring in a relatively short epidemic of about six weeks (2)

Reference:

• (1) Dawson-Caswell M, Muncie HL Jr. Respiratory syncytial virus infection in children. Am Fam Physician. 2011;83(2):141-6.
• (2) Immunisation Against Infectious Disease - "The Green Book". Chapter 27. Respiratory syncytial virus (January 2013)