TABLE 3.

Comparative features of respiratory viral infections during infancya

ParameterVirus
RSVRVInfluenza virus
Estimated occurrence rate688/1,000 (infected 1st yr), 826/1,000 (infected 2nd yr)0.51/child/mo5-30% outpatients, 0.1% inpatients
SeasonalityWinter (October-March)Fall and SpringEpidemics
Effect of glucocorticoidsNone observedPossible reduction in wheezeNone observed
SeverityCan cause bronchiolitis requiring hospitalizationCan cause bronchiolitis requiring hospitalizationCan cause bronchiolitis requiring hospitalization
ControlSpecific antibody (palivizumab)Nothing currentlySeasonal vaccine
Antiviral drug (ribavirin)Antiviral drugs (oseltamivir and zanamivir)
Genetic risk factorsAntiviral genes reduce severityLimited studies but suggestion that cytokine genes are importantLimited studies
Immune response genes increase severity
Host viral detectionRIG-I, TLR3, TLR4TLR3RIG-I, TLR3, TLR7, NLRP3, Casp-1
Viral host evasionInhibits RIG-I, IRF-3, STATInhibits MDA5, IRF-3Inhibits RIG-I
ImmunopathologyStrong associationEvidence of role of IL-8Cytokine storm
AsthmaAssociated with later-life wheeze and exacerbationsAssociated with later-life wheeze and exacerbationsAssociated with exacerbations
  • a The table compares the 3 most common viruses occurring in infants and summarizes various aspects described in detail in this review.