Lessons from two linked clusters of acute hepatitis B in cardiothoracic surgery patients.

Two clusters of acute hepatitis B in cardiothoracic surgery patients of two hospitals in the United Kingdom were investigated in 1992 and 1993. The source, a surgeon carrier of hepatitis B virus (HBV) whose serum contained hepatitis B e antigen (HBeAg), was not identified during investigation of the first cluster, although all the health care workers who had performed exposure prone procedures on the infected patients were tested. The HBV status of the surgeon, who was linked epidemiologically and virologically with cases in both clusters, was revealed only during the second investigation, when specimens were obtained directly from the surgeon and the other health care workers involved. Forensic testing showed the blood specimen provided by the surgeon during the first investigation to be distinct from that obtained directly from the surgeon during the second investigation; it later became clear that during the first investigation the surgeon had provided a specimen from a person likely to be hepatitis B surface antigen (HBsAg) negative. Patients on whom the surgeon had performed exposure prone procedures in the 15 months before the surgeon's infectivity was recognised were identified from local records, and those not known to have died or to be resident outside the United Kingdom were subsequently tested for markers of hepatitis B infection at least six months after exposure. In total, 310 of 323 (95%) exposed patients were tested; 20 (6%) were classified as having acquired hepatitis B infection in association with surgery, three of whom developed persistent infection. Two hundred and thirty-nine of the exposed and tested patients had undergone coronary artery replacement surgery with or without heart valve replacement. Thirteen out of 75 (17%) for whom the surgeon had taken the role of first assistant-which usually includes performing sternotomy -became infected, compared with five out of 159 (3%) of those for whom the infected surgeon acted as 'vein harvester' and would have been unlikely to have performed the sternotomy (p = 0.00029). We conclude that patients may be exposed to the blood of at least one operator in as many as one in six cardiothoracic surgery procedures that carry a high exposure risk. We suggest that blood specimens from health care workers should be obtained by directly observed sampling in the investigation of cases of acute hepatitis B infection that may have been acquired during surgery.