Respiratory Syncytial Virus Bronchiolitis in Infants Amanda Snodgrass Dr. Bill Grimes, Advisor Spring 2006

Objectives  Mechanisms involved in RSV infection and severity  Risk factors for severe RSV infection  Prophylaxis and treatment of RSV  Morbidity and Mortality

Case Study

RSV Facts  Most common cause of bronchiolitis & pneumonia in children under 1  25-40% of children develop bronchiolitis or pneumonia during first RSV infection  31/1,000 under 1 yr. are hospitalized with RSV  2% will die

Presentation  Cold-like sx  Audible wheezing  SOB  Anorexia  Poor sleeping  Irritability  Vomiting  Choking

Pathophysiology  Negative-strand RNA virus  Family Paramyxoviridae  RSV season late fall to early spring  Peak in January/February  Incubation 4-5 days, LRI between days 5-7

Severity of RSV Infection is Determined By:  Inhibition of certain interferons  Involvement of innate immune system  Interleukins and chemokines  Coinfection with other respiratory viruses

Inhibition of Interferons  Interferons believed to have antiviral properties  NS1 & NS2 inhibit IFN- alpha/beta  Inhibition of IFN-gamma causes enhanced IgE production

Innate Immune System  Activation contributes to inflammation & injury  RSV-F glycoprotein may inhibit T-cell activation  RSV-infected CD8+ cells unable to release IFN-gamma

Interleukins & Chemokines  Infection induces expression  Chemokines mimic RSV glycoproteins  Recruit monocytes, eosinophils, & neutrophils  IL-8 levels positively associated with severity

Coinfection  Rhinovirus contributes to increased severity in children with bronchiolitis  Metapneumovirus (hMPV) enhances or mimics symptoms of RSV bronchiolitis  70% were coinfected w/ hMPV & required amission to PICU

Risk Factors

Premature Birth  Likely to have chronic lung disease  Hypersensitive to stimuli  Underdeveloped airway & immunity  Lack adult maternal levels of IgG

CHD  Are more often hospitalized  Are more often admitted to PICU  Are more likely to die  Complications from pulmonary hypertension and increased hypoxia

Environmental & Demographics  Male infants  Age & birth month of infant  Crowding & day care attendance  Secondhand smoke

Factors NOT Positively Correlated  Socioeconomic status  Malnourishment  Breastfeeding

Prophylaxis  RSV-IGIV (RespiGam)  Children under 24 mo. w/ CHD or less than 35 wks. Gestation  Given IV monthly during RSV season  Volume overload possible  Not for infants w/ hemodynamically significant heart disease.

Prophylaxis  Palivizumab (Synagis)  Given IM monthly  Can reduce hospitalization of high risk infants by 45%  Expensive  Many providers reluctant to give  Many parents unaware

Treatment  Mostly symptomatic  Salbutamol MDI drug of choice  Also use epinephrine, ipratropium bromide, & oral steroids only if hospitalized

Morbidity & Mortality  More likely to visit a specialist  More likely to use respiratory therapy  More likely to receive diagnostic or therapeutic procedures  More likely to be hospitalized again  Subsequent hospitalization will be 3x as long

Morbidity & Mortality  More likely to suffer recurrent infections  Many have recurrent acute otitis media  Many likely to be hospitalized with another episode of acute respiratory distress

Morbidity & Mortality  Adolescents suffer from allergic asthma, allergic rhinoconjunctivitis, & more sensitive to inhaled allergens  More likely to have asthma, bronchial reactivity to methacholine, and reduced lung function  RSV ind. risk factor for reduced FEV% (FEV1/FVC)

Follow Up

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