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Clinical and Microbiologic Features Associated With Novel Swine-Origin Influenza A Pandemic 2009 (H1N1) Virus in Children: A Prospective Cohort Study

Bryant, Penelope A. MA, BM BCh, MRCP, MRCPCH, PhD*†‡; Tebruegge, Marc DTM&H, DLSHTM, MRCPCH, MSc, MD*†‡; Papadakis, Georgina BSc§; Clarke, Caroline DM, FRACP, MRCP*; Barnett, Peter MB BS, FRACP, MSc, FACEM, MSpMed*†‡; Daley, Andrew J. MB BS, MMed(ClinEpi), BAppSc(MLS), Dip Paed, FRACP, FRCPA*†; South, Mike MB BS, DCH, MRCP(UK), FRACP, FJFICM, FCICM, MD*†‡; Curtis, Nigel MA, MB BS, DCH, DTM&H, MRCP, FRCPCH, PhD*†‡

The Pediatric Infectious Disease Journal: August 2010 - Volume 29 - Issue 8 - p 694-698
doi: 10.1097/INF.0b013e3181de4b9c
Original Studies

Background: Novel swine-origin influenza A pandemic 2009 (H1N1) virus (S-OIV) infection in the context of other respiratory viruses circulating in winter has not been studied.

Methods: Clinical and microbiologic data were collected prospectively from 444 consecutive patients presenting with an influenza-like illness (ILI) to a large pediatric hospital at the beginning of the S-OIV outbreak in Australia.

Results: Of 444 patients, 119 had polymerase chain reaction-confirmed S-OIV. Influenza A virus was detected by direct immunofluorescence in only 69 of these. Overall, inadequate respiratory samples were more common with rayon than flocked swabs (P = 0.01). The mean age of patients with S-OIV was higher than those with another cause of an ILI (10.2 vs. 6.4 years; P < 0.0001). The commonest symptoms in S-OIV were fever (93%) and cough (92%), followed by coryza (78%), sore throat (72%), headache (59%), myalgia (49%), vomiting (23%), and diarrhea (16%). Clinical features did not discriminate between patients with S-OIV and those with another ILI, except headache and myalgia, which were more common in children younger than 5 years who had S-OIV than those who did not (headache: P < 0.0001; myalgia: P = 0.0004). More patients with S-OIV had contact with a confirmed case but contact history had insufficient positive predictive value (44%) and negative predictive value (78%) for identifying S-OIV. Only 2% of the patients had a history of travel, and only 1 of these had S-OIV.

Conclusions: A clinical case definition is unlikely to be useful for discriminating patients with S-OIV from those with another cause of an ILI during winter. Direct immunofluorescence for influenza A cannot be used alone to reliably detect S-OIV.


From the *The Royal Children's Hospital Melbourne, Parkville, Victoria, Australia; †Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia; ‡Murdoch Children's Research Institute, Parkville, Victoria, Australia; and §Victorian Infectious Diseases Reference Laboratory, Royal Parade, Parkville, Victoria, Australia.

Accepted for publication March 5, 2010.

All authors declare that they have no competing interests.

Address for correspondence: Nigel Curtis, MA, MB BS, DCH, DTM&H, MRCP, FRCPCH, PhD, Department of Paediatrics, The University of Melbourne, The Royal Children's Hospital Melbourne, Parkville, Victoria 3052, Australia. E-mail:

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© 2010 Lippincott Williams & Wilkins, Inc.