Abstract

BACKGROUND--Pneumocystis carinii pneumonia was thought to occur from reactivation of latent infection, but recent studies with the polymerase chain reaction have failed to detect P carinii in normal subjects. If pneumocystis pneumonia is therefore caused by new infection the source and mode of transmission of P carinii remains unknown. METHODS--Natural exposure to P carinii was detected by measuring antibodies by indirect immunofluorescence in 24 health care workers working continuously with patients with AIDS and 24 control health care workers exclusively treating elderly patients. RESULTS--P carinii antibody titres were significantly higher in the health care workers exposed to AIDS than in the control group (median titre 1:32 v 1:16 respectively). Three control subjects had no antibodies compared with none of the subjects exposed to AIDS, and 10 of the 12 highest titres came from the exposed group. CONCLUSIONS--Raised P carinii antibody titres in health care workers caring for patients with AIDS suggest that patients infected with HIV may be a potentially infectious source of P carinii for susceptible subjects.