Risk factors for severe illness

Clinicians should take into account the following risk factors for more serious illness when assessing and managing infants with bronchiolitis:

• Gestational age <37 weeks*;
• Younger chronological age at presentation*;
• Prenatal and/or postnatal exposure to tobacco smoke*;
• Reduced breastfeeding exposure*;
• Faltering growth/ slow weight gain (failure to thrive);
• Comorbidities including congenital heart disease, chronic lung disease, chronic neurological condition, congenital diaphragmatic hernia, trisomy 21, and other genetic disorders;
• Being an Indigenous infant†;
• Being an economically disadvantaged infant;
• Timing and severity of illness onset at hospital presentation. 

*Clinicians should judge these as risk factors on a continuous scale; with higher risk of poor outcomes associated with lower gestational age, lower chronological age, fewer days of breastfeeding exposure, and greater tobacco smoke exposure.

†Indigenous status, in itself, is unlikely to confer risk but there remains a correlation in Australia and Aotearoa New Zealand with ethnicity and severe bronchiolitis outcomes, independent of socioeconomic status, potentially reflecting the ongoing impacts of colonisation, remote geographical isolation and the institutional racism in our health systems. (Evidence quality: moderate; recommendation strength: strong)

Infants with any of these risk factors are more likely to deteriorate rapidly and require escalation of care. Risk factors are likely to be cumulative. Infants with bronchiolitis presenting with these risk factors may require a longer period of observation or hospital admission, even if they are presenting early in the illness with mild symptoms.