An emerging viral pathogen causing pyelonephritis in kidney allografts is -
High-Yield Explanation
Diseases caused by human polyomavirus infections are most common among immunocompromised people; disease associations include BK virus with nephropathy in renal transplant and non-renal solid organ transplant patients, JC virus with progressive multifocal leukoencephalopathy, and Merkel cell virus (MCV) Ref Davidson 23rd edition pg 877