Respiratory syncytial virus infection: Clinical features and diagnosis
Authors: Frederick E Barr, MD, Barney S Graham, MD, PhD
Section Editors: Morven S Edwards, MD, Gregory Redding, MD
Deputy Editor: Mary M Torchia, MD
All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Jun 2018. | This topic last updated: Jun 02, 2018.
INTRODUCTION — Respiratory syncytial virus (RSV) causes acute respiratory tract illness in persons of all
ages. The clinical manifestations vary with age, health status, and whether the infection is primary or secondary.
The epidemiology, microbiology, clinical manifestations, and diagnosis of RSV infection will be presented here.
The treatment and prevention of RSV infection and the treatment of bronchiolitis are discussed separately. (See
"Respiratory syncytial virus infection: Treatment" and "Respiratory syncytial virus infection: Prevention" and
"Bronchiolitis in infants and children: Treatment, outcome, and prevention".)
EPIDEMIOLOGY
Seasonality — RSV causes seasonal outbreaks throughout the world. In the northern hemisphere, these usually
occur from October or November to April or May, with a peak in January or February [1-3]. In the southern
hemisphere, wintertime epidemics occur from May to September, with a peak in May, June, or July. In tropical
and semitropical climates, the seasonal outbreaks usually are associated with the rainy season. The epidemic
peaks are not as sharp as in temperate climates, and in some settings RSV can be isolated in as many as eight
months of the year [4-7].
Morbidity — RSV causes acute respiratory tract illness in persons of all ages. Almost all children are infected by
two years of age, and reinfection is common [8].
In children — RSV is the most common cause of lower respiratory tract infection (LRTI) in children younger
than one year [1]. In a systematic review and meta-analysis, the global annual rate of RSV hospitalization among
children <5 years was 4.4 per 1000 (95% CI 3.0-6.4) [9]. RSV hospitalization rates were highest among children
<6 months (20.0 per 1000, 95% CI 0.7-41.3) and premature infants <1 year (63.9 per 1000, 95% CI 37.5-109.7).
In the United States between 1997 and 2006, the annual average rate of RSV hospitalization among children <5
years of age was 6.7 per 1000 (95% CI 5.3-8.1) [10]. Although the RSV hospitalization rate was greatest among
infants <3 months (48.9 per 1000), 42 percent of total hospitalization occurred in children >6 months.
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Hospitalization for RSV infection also may occur in children >5 years, but these children typically have underlying
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medical problems (eg, neurologic disease, immunodeficiency, etc).
In adults — RSV is also a significant and often unrecognized cause of LRTI in both older adults and
immunosuppressed patients [11-16]. It is estimated that RSV may be responsible for as much as 25 percent of
excess wintertime mortality, previously attributed solely to influenza [17]. The epidemiology and clinical impact of
RSV was compared with influenza in a large prospective cohort study of respiratory illnesses in 608 healthy older
adult patients, 540 high-risk adults, and 1388 hospitalized patients [18]. Diagnostic testing for RSV and influenza
infection included culture, reverse-transcriptase polymerase chain reaction (RT-PCR), and serology. The study
results were significant for the following:
●
The annual incidence of RSV infection in the prospective cohorts averaged 5.5 percent and was relatively
constant during the four years and nearly twice that of influenza A.
●
RSV infection developed annually in 3 to 7 percent of the healthy older adults group and in 4 to 10 percent
in the high-risk group.
●
In the hospitalized cohort, RSV infection and influenza A resulted in comparable lengths of stay, need for
intensive care monitoring, and mortality (8 and 7 percent, respectively).
Acute respiratory disease caused by RSV is not restricted to pediatric and high-risk adult populations. Healthy
adults are infected repeatedly throughout their lives and typically have symptoms restricted to the upper
respiratory tract. In a study of 256 military trainees with respiratory symptoms, RSV infection was identified in 11
percent of patients through serologic testing and real-time polymerase chain reaction (PCR) [19]. Other identified
viral pathogens included adenovirus (48 percent), influenza (11 percent), parainfluenza (3 percent), and
enterovirus (<1 percent).
Mortality — RSV is an important cause of death in infants, young children, and adults older than 65 years.
Globally, RSV is estimated to cause as many as 2.3 percent of deaths among neonates 0 to 27 days of age, 6.7
percent of deaths among infants 28 to 364 days of age, and 1.6 percent of deaths among children one through
four years of age [20]. Among infants 28 to 364 days of age, RSV is estimated to cause more deaths than any
other single infectious agent with the exception of malaria. In resource-limited settings, RSV mortality occurs
primarily in term infants [21].
In the United States, RSV pneumonia causes approximately 2700 deaths per year, predominantly in adults ≥65
years of age [17]. The estimated annual RSV-associated pneumonia mortality rate is 7.2 per 100,000 person
years in adults ≥65 years, 3.1 per 100,000 person years in children <1 year, and <1 per 100,000 person years in
other age groups. In the United States and other resource-rich countries, most pediatric RSV deaths occur in
children born prematurely and those with underlying cardiopulmonary disease or other chronic conditions [21,22].
Risk factors — Patients at risk for lower respiratory tract disease include:
●
Infants younger than six months of age [23], particularly those who are born during the first half of the RSV
season, those attending daycare [24,25], and those with older siblings (who may have asymptomatic RSV
infection) [26,27] (see 'Transmission' below)
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