Age-Stratified Risk of Critical Illness in Young Children Presenting to the Emergency Department with Suspected Influenza

Abstract

To investigate the risk of critical illness by age group among young children without a chronic condition presenting to the emergency department (ED) with suspected influenza. Retrospective study of patients aged <2years presenting to the ED with suspected influenza (defined by diagnostic codes for influenza or influenza-like illness) from 2009 to 2017 in 49 hospitals in the Pediatric Health Information System. Patients with chronic conditions were excluded. The main clinical outcomes were intensive care unit (ICU) admission, ventilatory support, vasopressor administration, and mortality, which were compared independently by age group (<3months, 3 to <6months, 6 to <12months, and 12 to <24months). To compare outcomes by age, we estimated the prevalence of each outcome by age group after fitting logistic regression models to control for demographic differences between groups. A total of 55 986 children were studied. Overall admission and ICU admission rates were 20% and 2%, respectively. After adjustment for demographic variables, infants aged <3months had higher rates of ICU admission (2.7%; 95% CI, 2.0%-3.3%; P<.001 compared with other age groups) and ventilatory support (2.5%; 95% CI, 1.9%-3.2%; P<.001 compared with other age groups); however, there were no differences in vasopressor administration. The overall case fatality rate was low (0.007%) and thus could not be compared across age groups. Infants aged <3months with suspected influenza are at greatest risk for critical illness. Although critical illness is uncommon, these findings should be incorporated into acute management decisions, including the need for specified outpatient follow-up or hospitalization, and public health efforts should focus on prevention and disease-modifying interventions in this high-risk population.