To our knowledge this is the first study analysing the viral load of hMPV in COPD patients. We found a mean of 6.5 × 10 5 viral copies/ml in nasal lavage and 1.88 × 10 5 viral copies/ml in induced sputum. These values indicate that hMPV may have been the infectious agent triggering exacerbation in these patients. Viral load cut-off values for infectivity in COPD exacerbations have not been studied in detail yet and need further investigation. However, viral loads between 1120 copies/ml in Cytomegalovirus infection in lung-transplant patients [27] and 5.8log 10 copies/ ml in SARS [28] have been considered to indicate infectious disease. Moreover hMPV was only found in acute exacerbation and not in stable disease or in smokers without COPD supporting a triggering role in AE-COPD.