To investigate a cluster of hepatitis B virus (HBV) infections between December 1995 and May 1996 among chronic hemodialysis patients in one county.

Two dialysis centers (A and B) and a hospital (C) in one county.

Six case-patients who were dialyzed in one of two centers, A and B, and had all been hospitalized between January and February 1996 at hospital C.

Patient 1, usually dialyzed in center A sero-converted to hepatitis B surface antigen (HBsAg) in December 1995 and could have been the source of infection for the others, who seroconverted between March and April 1996. Two cohort studies were conducted: one among patients dialyzed in center A to determine where transmission had occurred, and one among patients dialyzed at hospital C at the time patient 1 was hospitalized, to identify factors associated with infection.

Four (15%) of the 26 susceptible patients dialyzed at center A became infected with HBV. Hospitalization at hospital C when patient 1 was hospitalized was associated with infection (P=.002). A cohort study of the 10 susceptible patients dialyzed at hospital C during the time patient 1 was hospitalized did not identify specific risk factors for infection. However, supplies and multidose vials were shared routinely among patients, providing opportunities for transmission.

When chronic hemodialysis patients require dialysis while hospitalized, their HBsAg status should be reviewed, and no instrument, supplies, or medications should be shared among them.