RSV bronchiolitis is a common lower respiratory tract infection in infants under 2 years old, characterized by wheezing. It is most often caused by the RSV virus. RSV spreads easily among children and causes seasonal epidemics in the winter. Symptoms range from mild to severe and include rhinorrhea, cough, wheezing and respiratory distress. Treatment focuses on supportive care and oxygen supplementation for severe or hypoxic cases. While most cases resolve without long term effects, some children may develop recurrent wheezing or asthma.

1. RSV Bronchiolitis
Anju Vijay – R2

2. DEFINITION
 Bronchiolitis is broadly defined as a clinical syndrome that occurs in children <2
years of age and is characterized by upper respiratory symptoms (eg, rhinorrhea)
followed by lower respiratory (eg, small airway/bronchiole) infection with
inflammation, which results in wheezing and or crackles (rales). Bronchiolitis
typically occurs with primary infection or reinfection with a viral pathogen, but
occasionally is caused by bacteria (eg, Mycoplasma pneumoniae). In young
children, the clinical syndrome of bronchiolitis may overlap with recurrent virus-
induced wheezing and acute viral-triggered asthma.

3. ETIOLOGY
 RSV is an enveloped RNA virus with a single-stranded negative sense genome that
replicates entirely in the cytoplasm of infected cells and matures by budding from
the apical surface of the cell membrane.
 The virus belongs to the family Paramyxoviridae, subfamily Pneumoviridae.
 There are 2 antigenic subgroups of RSV, based primarily on variation in 1 of the 2
surface proteins, the G glycoprotein that is responsible for attachment.
 This antigenic variation caused by point mutations from infidelity of the virus RNA
polymerase may to some degree contribute to the frequency with which RSV
reinfects children and adults.

4. EPIDEMIOLOGY
 RSV is distributed worldwide and appears in yearly epidemics. In temperate
climates, these epidemics occur each winter over 3 – 4 months.
 RSV outbreaks often overlaps with outbreaks of influenza and human
metapneumovirus but are more consistent from year to year and result in more
disease overall, especially in infants younger than 6 months of age.
 Transplacentally acquired anti RSV maternal IgG serum antibodies, if present in
high concentration, appear to provide partial but incomplete protection.
 Breastfeeding also provides substantial protection.

5.  Reinfection occurs at a rate of at least 10-20% per epidemic throughout childhood.
 The severity of illness in reinfection is usually lower and appears to be a function of partially acquired
immunity, more robust airway physiology and increased age.
 Asymptomatic RSV infection is unusual in young children.
 All RSV diseases of the lower respiratory tract have their highest incidence at 6 weeks – 7 months of age
and decrease thereafter.
 RSV plays a causative role in 40 – 75% cases of hospitalized bronchiolitis.
 RSV bronchiolitis is more common in boys than girls in the ratio of 1.5:1.
 Other risk factors include white race, 1 or more siblings in the home, rural residence, maternal smoking.

6.  The incubation period from exposure to first symptoms is approx. 3 – 5 days.
 Most infants with lower respiratory tract illness shed infectious virus for 1-2 weeks
after hospital admission. Excretion for 3 weeks and even longer has been
documented.
 Spread of infection occurs when large, infected droplets, either airborne or
conveyed on hands or other fomites, are inoculated in the nasopharynx of a
susceptible subject.
 Nosocomial infection during RSV epidemics is an important concern.
 Contact precautions are sufficient to prevent spread when compliance is
meticulous, as the virus is not usually spread by small particle aerosol.

7. PATHOGENESIS
 Bronchiolitis is caused by obstruction and collapse of the small airways during
expiration
 Infants are particularly apt to experience small airway obstruction due to the small
size of their normal bronchioles, airway resistance is proportional to 1/r4
 Airway narrowing likely is caused by virus induced necrosis of the bronchiolar
epithelium, hyper secretion of mucus, and round cell infiltration and edema of the
surrounding submucosa. These changes result in formation of mucus plugs
obstructing bronchioles, with consequent hyperinflation or collapse of the distal
lung tissue.
 The immune response required to eliminate virus infected cell causes host cell
death while reducing the cells producing virus.

8. CLINICAL MANIFESTATIONS
 Typically, the first sign of infection in infants with RSV is rhinorrhea. Cough may
appear simultaneously but more often does so after an interval of 1-3 days at
which time there may also be sneezing and a low grade fever.
 Soon after the cough develops the child begins to wheeze audibly.
 If the disease is mild, the symptoms may not progress beyond this stage.
 Auscultation often reveals diffuse fine inspiratory crackles and expiratory wheezes.
 Chest radiograph findings at this stage is frequently normal.

9.  If the illness progresses, cough and wheezing worsen and air hunger ensues, with
increased respiratory rate, intercostal and subcostal retractions, hyper expansion of
the chest , restlessness and peripheral cyanosis.
 Signs of severe life threatening illness are central cyanosis, tachypnea of > 70
breaths/min, listlessness and apneic spells. At this stage, the chest maybe
significantly hyperexpanded and almost silent to auscultation due to poor air
movement.
 CXR findings maybe normal in 30% of cases while the other 70% may show hyper
expansion of the chest, peribronchial thickening, and interstitial infiltrates.
 In young infants, particularly premature infants, periodic breathing and apneic
spells have been distressingly frequent signs even with relatively mild disease.

10. DIAGNOSIS
 Bronchiolitis is a clinical diagnosis.
 RSV can be suspected on the basis of the season of the year and the presence of virus in the
community.
 Other features which maybe helpful are the presence of cold in older household contacts and the
age of the child.
 The WBC count is normal or elevated, and the differential cell count maybe normal with either a
neutrophilic or mononuclear predominance.
 Hypoxemia as measured by pulse oximetry or ABG analysis is frequent.

11.  CXR may show hyperinflation with peribronchial thickening.
 Definitive diagnosis of RSV is based on the detection in respiratory secretions of
live virus by cell culture. The presence of viral RNA (detected by PCR) or viral
antigens (detected by a rapid diagnostic test) is strongly supportive in the right
clinical setting.
 An aspirate of mucus or nasopharyngeal wash from the child’s posterior nasal
cavity is the optimal specimen. Nasopharyngeal or throat swabs are less preferable
but acceptable.
 The specimen should be placed on ice taken directly to the lab and processed
immediately for culture, antigen or PCR analysis as the virus is thermo labile.

12. TREATMENT
 The treatment of uncomplicated cases of bronchiolitis is symptomatic.
 Humidified oxygen and suctioning are usually indicated for hospitalized patients
who are hypoxic.
 Many infants are slightly to moderately dehydrated, and therefore fluids should be
carefully administered in amounts somewhat greater than those for maintenance.
 Often IV or tube feeding is helpful when sucking is difficult because of tachypnea.
 Aerosolized saline or hypertonic saline , epinephrine or beta2 agonists is used as an
adjunct therapy.
 Combined therapy with inhaled epinephrine and dexamethasone has been used
with some success.
 Antibiotics are not useful in nearly all instances of bronchiolitis.

13. SEVERITY ASSESSMENT
 In general, we consider severe bronchiolitis to be indicated by any of the following:
●Persistently increased respiratory effort (tachypnea; nasal flaring; intercostal, subcostal, or
suprasternal retractions; accessory muscle use; grunting) as assessed during repeated
examinations separated by at least 15 minutes
●Hypoxemia (SpO2 <95 percent); SpO2 should be interpreted in the context of other clinical
signs, the state of the patient (eg, awake, asleep, coughing, etc), and altitude
●Apnea
●Acute respiratory failure
 We consider nonsevere bronchiolitis to be indicated by the absence of all of the above.
However, the severity categories may overlap and clinical judgment is necessary to
make appropriate management decisions.
 Repeated observations are necessary to adequately assess disease severity because
examination findings may vary substantially over time

14. NONSEVERE BRONCHIOLITIS
 Supportive care and anticipatory guidance are the mainstays of management of
non severe bronchiolitis.
 Supportive care includes maintenance of adequate hydration, relief of nasal
congestion/obstruction, and monitoring for disease progression.
 For infants and children with non severe bronchiolitis who are treated in the office
or emergency department, we suggest not routinely treating with nebulized
hypertonic saline.

15. SEVERE BRONCHIOLITIS
 Supportive care includes maintenance of adequate hydration, respiratory support,
and monitoring for disease progression.
 Fluid management
 Respiratory support – saturation > 92 %
 Nasal suctioning
 Supplemental oxygen
 Although we do not routinely suggest inhaled bronchodilators for the
management of bronchiolitis, a one-time trial of inhaled bronchodilators (albuterol
[salbutamol] or epinephrine) and glucocorticoids may be warranted for infants and
children with bronchiolitis and severe disease.

16. PROGNOSIS
 The mortality rate of hospitalized infants with RSV is very low in the developed
world.
 Almost all deaths occur among young, premature infants or infants with underlying
disease of the neuromuscular, pulmonary, cardiovascular or immunologic system.
 Many children with asthma have a history of bronchiolitis in infancy.
 There is recurrent wheezing in 30-50% of children with severe RSV bronchiolitis in
infancy.

17. PREVENTION
 In the hospital, the most important preventive measures are aimed at preventing
nosocomial spread.
 Gowns, gloves and careful hand washing should be used for the care of all infants
with suspected or established RSV infection.
 Ideally patients with RSV are housed separately, because coinfection maybe
associated with more severe disease.
 Palivizumab (15 mg/kg once a month) is recommended for protecting high risk
children against serious complications from RSV disease.
 There is no licensed vaccine against RSV.

18. REFERENCES
 Uptodate.com
 Nelson textbook of Pediatrics
 Harriet lane manual
 Medscape.com