Enhanced surveillance for serious complications of influenza in children: role of the Australian Paediatric Surveillance Unit.

Influenza contributes significantly to disease burden among children aged less than five years. Existing influenza surveillance systems do not provide detailed data on clinical presentation, management, vaccination status, risk factors and complications in hospitalised children, or link such data with laboratory results. Following a number of child deaths due to influenza in 2007, the Australian Government Department of Health and Ageing approached the Australian Paediatric Surveillance Unit (APSU) to examine the feasibility of enhancing APSU surveillance to identify children hospitalised with severe complications of influenza. Active, national, weekly surveillance was conducted during September 2007 with reporting by 1,256 Australian paediatricians working in hospitals and outpatient settings. The weekly report card return rate was 93%; detailed clinical data were provided on 88% of all notified cases and 15 children met the case criteria for severe complications of influenza. Admission to hospital occurred within 48 hours of onset of symptoms in over half of the children, of whom 13 had influenza A and two had influenza B, confirmed mostly by polymerase chain reaction on nasopharyngeal aspirate. Serious complications included pneumonia, presumed viral (67%), secondary bacterial infection, shock, cardiomyopathy, myocarditis and hypoglycaemia. No child aged six months or older had been vaccinated against influenza, including three children with underlying chronic conditions. No eligible child received an antiviral agent for influenza. Length of hospital stay ranged from 2 to 34 days; four children were admitted to a Paediatric Intensive Care Unit and one was ventilated. This study demonstrates the feasibility of using the established APSU mechanism for enhanced emergency surveillance during disease outbreaks, emergence or importation.