A 16-month-old presents to the clinic with her parents for c…

A 16-month-old presents to the clinic with her parents for cough. The father reports the child’s illness started 3 days ago with a runny nose but is now more of a cough. The child’s vital signs show a respiratory rate of 24 breaths per minute, temperature of 101.4°F, and oxygen saturation of 94%. There is mild wheezing on auscultation. You suspect a diagnosis of bronchiolitis. Which of the following would be a predictor of more severe disease?