Phylogenetic analyses indicate an atypical nurse-to-patient transmission of human immunodeficiency virus type 1

A human immunodeficiency virus (HIV)-negative patient with no risk factor e xperienced HIV type 1 (HIV-1) primary infection 4 weeks after being hospita lized for surgery. Among the medical staff, only two night shift nurses wer e identified as HIV-1 seropositive. No exposure to blood was evidenced. To test the hypothesis of a possible nurse-to-patient transmission, phylogenet ic analyses were conducted using two HIV-1 genomic regions (pol reverse tra nscriptase [RT] and env C2C4), each compared with reference strains and lar ge local control sets (57 RT and 41 C2C4 local controls). Extensive analyse s using multiple methodologies allowed us to test the robustness of phyloge ny inference and to assess transmission hypotheses. Results allow us to una mbiguously exclude one HIV-positive nurse and strongly suggest the other HI V-positive nurse as the source of infection of the patient.