Considering the seemingly higher prevalence of KIP-yV in our population (8%), immunocompromised patients may be more susceptible to this PyV, as they are to JC and BK viruses (13) (14) (15) . Results from previous reports suggest a similar frequency of both KIPyV and WUPyV infections being found in respiratory specimens, ranging from 1% to 3%. In contrast, in our series, we found a likely difference between the prevalence of KIPyV (8%) and WUPyV (1%), which suggests that the replication or reactivation of the 2 viruses in the respiratory tract may differ between immunocompromised and immunocompetent patients. However, this difference requires further investigation, in particular, by using similar real-time PCR assays. Notably, a significantly higher prevalence of KIPyV infection was found among HSCT patients, which suggests that a profound T-cell defi ciency may be a factor in facilitating KIPyV replication.