Lessons from a French collaborative case–control study in cystic fibrosis patients during the 2009 A/H1N1 influenza pandemy

BACKGROUND: Viral infections such as influenza are thought to impact respiratory parameters and to promote infection with Pseudomonas aeruginosa in patients with cystic fibrosis (CF). However, the real morbidity of the influenza virus in CF needs to be further investigated because previous studies were only observational. METHODS: CF patients were included in a case–control study (n = 44 cases and n = 371 controls) during the 2009 pandemic A/H1N1 influenza. Cases were patients with polymerase reaction chain-confirmed influenza A/H1N1 infection. Controls did not report any influenza symptoms during the same period. Sputum colonization and lung function were monitored during 1 year after inclusion. RESULTS: Cases were significantly younger than controls (mean(SD) 14.9 years(11) versus 20.1 years (13.2) and significantly less frequently colonized with P. aeruginosa (34 % versus 53 %). During influenza infection, 74 % of cases had pulmonary exacerbation, 92 % had antibiotics adapted to their usual sputum colonization and 82 % were treated with oseltamivir. Two cases required lung transplantation after A/H1N1 infection (one had not received oseltamivir and the other one had been treated late). The cases received a mean number of antibiotic treatments significantly higher during the year after the influenza infection (mean(SD) 2.8 (2.4) for cases versus 1.8(2.1) for controls; p = 0.002). An age-matched comparison did not demonstrate any significant modification of bronchopulmonary bacterial colonization during the year after influenza infection nor any significant change in FEV1 at months 1, 3 and 12 after A/H1N1 infection. CONCLUSIONS: Our results do not demonstrate any change in sputum colonization nor significant lung disease progression after pandemic A/H1N1 influenza. TRIAL REGISTRATION: Clinical Trials.gov registration number: NCT01499914