Lessons from a French collaborative case–control study in cystic fibrosis patients during the 2009 A/H1N1 influenza pandemy
BACKGROUND Influenza, like other respiratory viral infections, can cause acute deterioration of lung function in patients with cystic fibrosis (CF). Previous studies on a small number of patients reported that most people with CF infected with A (H1N1) influenza experienced a mild course of disease. AIM To characterise the impact of A (H1N1) infection on CF in a large number of patients from different centres and countries. METHODS CF centres accessing the web-site of the European Cystic Fibrosis Society (ECFS) were asked to report clinical data on patients with an ascertained diagnosis of influenza caused by the A (H1N1) virus. The study was web-based and data were collected through an electronic data sheet on the ECFS website. RESULTS Twenty-five centres from 10 countries caring for 4698 patients with CF reported data on 110 patients (2.3%), median age 13 years (range 1-39 years). The prevalence of infection in each centre ranged from 0% to 9.4%. Only 8.8% of the patients had been vaccinated. The main symptoms were fever and respiratory exacerbation requiring IV antibiotics in 53% of the patients; 48% of the patients were hospitalised for an average of 12.9 days (range 2-56) and 31% required oxygen treatment during the time of the infection. Most of the patients recovered and FEV(1) 1 month after the infection was similar to that before the infection. However, 6 patients were admitted to ICU, 5 with mechanical ventilation. Three patients with severe respiratory disease died. CONCLUSIONS A (H1N1) influenza infection caused transient but significant morbidity in most of the patients with CF. However, in a small number of patients with severe lung disease, A (H1N1) influenza was associated with respiratory deterioration, mechanical ventilation and even death.