Pseudomonas aeruginosa is one of the most important pathogens in the context of CF (2). Infections with P. aeruginosa can be distinguished into two different groups: (i). intermittent infections in which the infection with P. aeruginosa can be cleared by antipseudomonal treatment, (ii). chronic infections in which P. aeruginosa can be isolated from most of the respiratory samples indicating that the respiratory tract is chronically colonized by this bacterium (26). Infections with P. aeruginosa are correlated with an accelerated decline in lung function and with an increased incidence of respiratory exacerbations (27, 28). Viral infections have been linked to exacerbations in other chronic pulmonary diseases and respiratory virus infections in CF patients seem to be associated with higher viral burden and higher morbidity (29). Investigation of the link between P. aeruginosa and respiratory viruses could therefore identify potential new therapeutic and diagnostic strategies.