(HealthDay News) — More than one in three children presenting to the emergency department with influenza-like illness develop severe complications, according to a study published online Aug. 4 in Pediatrics.

Rakesh D. Mistry, MD, from the University of Colorado School of Medicine in Aurora, and colleagues examined the development of severe complications in a prospective study of children presenting to the emergency department for moderate to severe influenza-like illness. Data were collected from 241 enrolled subjects with a median age of 27.4 months. Patients had moderate to severe influenza-like illness, defined by performance of venipuncture and nasopharyngeal multiplex polymerase chain reaction for respiratory viruses.

The researchers found that more than half of the participants (53.5%) had high-risk conditions. Severe complications developed in 35.3%, with pneumonia (26.1%) the most frequent complication. Subjects with neurologic or neuromuscular conditions had increased risk for severe complications (relative risk [RR], 4.0; 95% confidence interval [CI], 1.9–8.2). The development of severe complications was not associated with a specific respiratory virus. Among patients with influenza, those with subtype H1N1 had increased risk of severe complications (RR, 1.45; 95% CI, 0.99–2.13; P=0.048) and the highest risk of pneumonia (RR, 4.2; 95% CI, 1.2–15.9).

“Although most children presenting with respiratory illnesses during peak influenza seasons manifest uncomplicated influenza-like illness, as many as one in three children presenting with more acute illness are at high risk for development of severe, complicated illness,” the authors write.

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