RESUMEN
<b>Objective</b> To evaluate the effect of irregular follow-up during normalized prevention and control of novel coronavirus pneumonia (COVID-19) epidemic on BK virus (BKV) reactivation and clinical prognosis of kidney transplant recipients. <b>Methods</b> Clinical data of 363 kidney transplant recipients were retrospectively analyzed, and they were divided into the pre-epidemic follow-up group and during-epidemic follow-up group according to the follow-up time. All patients were followed up for 1 year. The follow-up interval was compared between two groups. The infection of BKV and the correlation between the infection process of BKV and renal graft function were analyzed in two groups. <b>Results</b> A total of 1 790 preson-times were followed up before COVID-19 epidemic and 2 680 during COVID-19 epidemic. Compared with the during-epidemic follow-up group, the follow-up intervals within 3, 3-6 and 7-12 months after kidney transplantation were shorter in the pre-epidemic follow-up group, and the differences were statistically significant (all <i>P</i><0.05). Within 1 year after kidney transplantation, 35 cases（32%） were diagnosed with BKV viruria, 3 cases（3%） of BKV viremia and 1 case（1%） of BKV-associated nephropathy (BKVAN) in the pre-epidemic follow-up group, and 53（25%）, 3（1%） and 1（1%） in the during-epidemic follow-up group, with no statistical significance (all <i>P</i>>0.05). In the pre-epidemic follow-up group, the time for the initial diagnosis of BKV viruria was longer and the viral load of the first urinary BKV reactivation was smaller than those in the during-epidemic follow-up group, with statistical significance (both <i>P</i><0.05). The load of the first urinary BKV reactivation was positively correlated with the peak load of urinary BKV, and the differences between the baseline and serum creatinine levels at 1 and 3 months after BKV reactivation (all <i>P</i><0.05). <b>Conclusions</b> Irregular follow-up after kidney transplantation may lead to early BKV reactivation and higher detection value of the first viral load of urinary BKV, delay diagnosis and interventions, and lead to poor prognosis. It is urgent to establish a remote follow-up system to meet the follow-up requirements of kidney transplant recipients when public health incidents occur.