Background Recently, three new polyomaviruses—KI, WU and Merkel cell (MCV)—have been discovered and their detection has been reported in different types of specimens, including respiratory samples, suggesting their shedding in the airways. In lung graft recipients, viral agents are associated with events that may limit the success of transplantation, including organ infection/disease and allograft rejection.

Aims To evaluate the prevalence of KI, WU and MCV in transbronchial biopsies from lung transplant recipients and investigate the association with clinical and histopathological features.

Methods The quantitation of new polyomaviruses DNA by real-time PCR and association with clinical and histopathological findings were evaluated in 66 transbronchial biopsies from lung transplant recipients.

Results KI, WU and MCV were detected in 9.2%, 12.3% and 33.8% of specimens, respectively; with mean viral load ranging from 81 copies/10⁴ cells for WU to 258 for MCV, thus not differing from that previously reported in native lungs. No significant association with clinical and histopathological findings (including acute respiratory insufficiency, interstitial and organising pneumonia, acute and chronic rejection) was found.

Conclusions Results showed a relatively high frequency of detection of the novel polyomaviruses in transbronchial biopsies from lung transplant recipients. It is likely that this accounted for the positive results found in some cases with different pathological background, although no significant association with a specific clinical and/or histopathological pattern was found.