Infections may be bacterial (eg, listeriosis, nocardiosis), viral (eg, due to BK virus [a common opportunistic polyomavirus in kidney transplant recipients], CMV, Epstein-Barr virus, varicella-zoster virus, or hepatitis B or hepatitis C virus), fungal (eg, aspergillosis, cryptococcosis, Pneumocystis jirovecii infection), or parasitic (eg, strongyloidiasis, toxoplasmosis, trypanosomiasis, leishmaniasis).