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Respiratory Syncytial Virus

  • Definition

    RSV is a virus that is a major cause of bronchiolitis and pneumonia during infancy and early childhood.


    It induces formation of large syncytial masses in cell cultures, and this led to its being so named.

    When a child under two years of age presents in midwinter with a runny nose, dry cough, and mild to moderate fever, chances are that he or she has respiratory syncytial virus infection (RSV).

    Although the illness usually runs its course in two to three weeks, infection can be life-threatening in very young infants and those with high-risk conditions such as congenital heart disease.

    RSV usually causes cases of bronchiolitis (inflammation of the air passages) in infants. Most hospitalizations occur in infants between one and six months old.

    The virus is endemic in nature and commonly causes reinfection because immunity to it is short-lived. Reinfections are generally benign in adults; however, in elderly and immunocompromised patients, serious disease of the lower respiratory tract may result.

    Illness from RSV occurs in epidemics, particularly in temperate climates, starting in fall and continuing until spring, with a peak incidence of infection usually occurring in winter. RSV has been isolated in 45 to 75 percent of patients who have bronchiolitis, 15 to 25 percent of childhood pneumonias, and 6 to 8 percent of cases of croup.


    RSV infections are mainly as a result of inoculation (introduction into the body) from hand to eye, nose, and other mucous membranes; they also occur by direct inoculation by large-particle aerosols or by self-inoculation from contaminated organisms. RSV has been recovered from countertops for up to six hours after contamination and from skin for as long as 20 minutes.

    Infected persons shed the virus for up to 27 days, a period that carries with it substantial potential for nosocomial (a new disorder, unrelated to the patient's primary condition, associated with being treated in a hospital) spread.

    RSV infection is slightly more common in boys than girls. Racial factors make little difference. Daycare centers are one site of infection and reinfection.


    After an incubation period of 3 to 7 days, RSV infection presents with one to two days of rhinitis (inflammation of the nasal membranes), dry cough, and mild to moderate fever. In 30 to 40 percent of cases, infection progresses to involve the lower respiratory tract, with subsequent development of bronchiolitis and pneumonia.

    Lower respiratory tract involvement is indicated by the onset of expiratory wheezing or inspiratory sounds, marked cough, tachypnea (rapid breathing) and retractions (heavy breathing), and varying degrees of cyanosis (bluish/purple color of the skin).

    In neonates, another presentation may occur, with apnea (stopped breathing), lethargy, and a decrease in appetite as the predominant symptoms.

    In infants with upper respiratory tract symptoms only, the process generally resolves in 4 to 7 days, much like an ordinary cold.

    In patients with lower tract involvement, an uncomplicated course may run 7 to 21 days before all symptoms resolve. The hospitalization rate for infants with lower respiratory tract involvement is 2 percent to 6 percent, but this drops to only 0.5 percent if all cases of upper and lower respiratory tract disease are considered.

    Secondary bacterial infections, especially otitis media (ear infection) and pneumonia are common. These should be suspected if the course is prolonged or an acute fever follows earlier defervescence (lowering of an elevated temperature).


    Diagnosis is based on the medical history including symptoms, patient age, and time of the year, as well as the physical exam. Lab tests to detect RSV (by a swab from the nasal cavity or throat) may be performed. A chest x-ray may be done.


    The parents of infants who are mildly ill with RSV infection can be given reassurance. Outpatient treatment consists of supportive measures, such as increased intake of clear liquids and use of acetaminophen for fever. Humidification with cool mist may be recommended.

    Parents are often instructed to return or call the office if the infant's breathing becomes more labored, cyanosis or apnea develops, or oral intake is impaired. In most cases, antibiotics are not useful. Severe cases of RSV infection, especially in high-risk infants, may require hospitalization. Ribavirin, an aerosolized treatment for severe RSV, can be considered early in the course of the infection.


    Will this make the child more susceptible to developing bronchiolitis in the future?

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    Will you be prescribing any medication? What are the side effects?

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