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We studied the incidence of staphylococcal infection in a thoracic surgery ward which consisted of a number of separate rooms, and inquired whether the subdivision of the ward was responsible for the unusually low sepsis-rate.The airborne dissemination of Staphylococcus aureus from one room to another appeared to be little less than that in an open ward; but the total number of Staph. aureus in the air was very low.Most of the patients received prophylactic antibiotics. The nasal carrier-rate of Staph. aureus by patients fell greatly during their stay in the ward. There was a progressive disappearance of sensitive organisms and little acquisition of multiple-resistant organisms.When there are urgent clinical grounds for the lavish use of antibiotics, the dangers appear to be reduced by effective segregation of the patients from each other.

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The frequency of transmission of hepatitis B virus infection from health service staff to patients was assessed from reports of confirmed cases of acute clinical hepatitis in 1980-3. During the four years 4505 reports (91% of the total) included replies to a question about recent operations; 153 patients (3.4%) had this history. Transfused blood or blood products were considered the source for 27 cases (0-06%). Eleven patients (0-02%) were infected in two clusters, both in cardiac surgery units; six were caused by a perfusion technician, who was a symptomless carrier, and five by a surgical registrar during the incubation period of an acute hepatitis B infection. The estimated average annual risk of a patient developing acute hepatitis B as part of a cluster caused by staff during surgical procedures was one in a million operations. For another 11 patients blood transfusion could not be excluded as a source. Where no association between surgery and hepatitis was found the incidence of a history, lay between 2-3 and 2.6%. The Hospital In-Patient Enquiry data showed that about 2-4% of the population had had operations in a six month period.These findings suggest that transmission of hepatitis B infection from staffto patients is rare in Britain and that the small risk could be eliminated by attention to measures to preserve asepsis and by immunising staff at risk. IntroductionThe acquisition of hepatitis B infection by health service staff from patients is an occupational hazard, the size of which can be estimated by comparing infection rates in health service staff with those in the general population.' 2 Reports of transmission in the other direction-that is, from staff to patients-are uncommon, and attempts to assess their frequency were considered unnecessary in Britain, where both the incidence of acute hepatitis B and the prevalence of hepatitis B surface antigen (HBsAg) carriage are low. After an outbreak of acute hepatitis B among patients, however, which was caused by a gynaecologist who was a symptomless carrier of the infection,3 a study was designed to estimate the frequency of such events. A similar episode, which was discovered in England and investigated locally before plans for the national study were completed, emphasised the need for the investigation (Anonymous Control of Infection Team, unpublished observations).We decided to make a nationwide study based on confirmed cases of acute hepatitis B which are reported from laboratories through-

SUMMARYAn investigation was made of nasal acquisition of Staphylococcus aureus and of staphylococcal wound sepsis in a hospital ward divided into two sections and provided with mechanical ventilation, so that there was no transfer of air from one of the sections to the other. Although the strains of S. aureus found in the air, and those colonizing the noses of patients, in the protected section could seldom be related to patients nursed elsewhere in the ward, the mechanical ventilation did not lead to any significant reduction in the degree of contamination of the air or in the rate of nasal acquisition of S. aureus.Even in the protected section, nearly 20 % of the strains of S. aureus recovered from the air could not be related to known nasal carriers. Since this proportion was nearly as great as that found in the absence of directed air-flow, it seems probable that these strains were derived either from undetected sources within the section or were dispersed from the clothes of persons who entered it.Nearly one-third of the nasal acquisitions in the ward could not be related to known nasal carriers, but about one-half of these (16 %) were probably 'spurious' and half of the remainder (8 %) could be related to strains recovered from patients' lesions or drawsheets, leaving no more than 8 % unaccounted for. A short investigation in which both drawsheet and perineal samples were examined showed that drawsheet samples did not give a reliable indication of perineal carriage unassociated with nasal carriage. During the period of the investigation, a single strain of S. aureus that was resistant to a wide range of antibiotics established itself in the ward. The most notable character of this strain was the profuse dispersion of it by carriers. As a consequence, staphylococcal wound sepsis increased, with nearly three-quarters of 0. M. LIDWELL AND OTHERS the infections attributable to this strain, and nasal carrier rates increased with length of stay in the ward, over 20 % of patients who stayed 5-6 weeks acquiring the strain.