[BK virus infections in kidney transplantation]

BK virus is near ubiquitous, with a seroprevalence of around 80% in the general population. Subsequent to an asymptomatic primary infection, BK virus then remains dormant in healthy subjects. Reactivation occurs in immunocompromised people. BKv is pathogenic mainly among patients who have received a kidney transplant, in whom the virus can cause specific tubulo-interstitial nephritis and even result in graft failure among approximately 20 to 30% of nephritic cases. Since the mid 90 s, incidence has increased with the use of new powerful immunosuppressor treatments. The cornerstone of BK virus infection or BK virus-associated nephropathy treatment is a decrease of the immunosuppressive regimen, which must then be offset with the risk of rejection. The use of several adjuvant therapies has been submitted (fluoroquinolones, leflunomide, intravenous immunoglobulins, cidofovir), with no sufficient proof enabling the recommendation of first-line prescription. The high frequency of this infection and its potential harmfulness argue for the use of prevention strategies, at least among patients presenting risk factors. Retransplantation is safe after a first kidney allograft loss caused by BK-virus nephropathy, on condition that a screening for viremia is frequently conducted.