R - organism

- R africae - R burnetii - R equi - R honei - R intestinalis - R prowazekii - R rickettsii - R sibirica - R tsutsugamushi - rabbit hutch spider - rabies virus - Rapidly growing mycobacteria - rapidly-growing Mycobacterium - Rat lungworm - rat tapeworm - redback spider - Reduviidae - Reoviridae - respiratory syncytial virus - Retortamonas intestinalis - Retroviral - Retroviridae - Retrovirus - Rhinovirus - Rhodococcus equi - Richettsia - Richettsia burnetii - Richettsia honei - Richettsia rickettsii - Richettsia sibirica - Rickettsia - Rickettsia africae - Rickettsia honei - Rickettsia prowazekii - Rickettsia rickettsii - Rickettsia sibirica - Rickettsia spotted fever group - Rickettsia tsutsugamushi - Rickettsia typhus group - Rickettsiae - Rickettsial - Rift Valley fever virus - Rikenellaceae - river blindness worm - Rochalimaea - Rochalimaea henselae - Rochalimaea quintana - Rochalimaea vinconii - Rocio virus - Ross river virus - Rotavirus - RSV - rubella virus - rubeola - Ruminococcaceae - Ruminococcus - Russian Spring Summer encephalitis virus