COPD is a progressive disease whom course is characterized by repeated exacerbations, with a negative impact on quality of life and health costs. Although a causal link between the identification of viruses in the upper respiratory tract and exacerbation is not definitively established, there is growing evidence that viruses are important triggers of exacerbations in more than 50 percent of cases. Yet, neither clinical presentation nor biological markers permit to discriminate between viral and non viral exacerbations.