[Hospital outbreak of Mycobacterium tuberculosis resulting from autopsy exposure]

An epidemic outbreak of tuberculosis resulting from exposure at an autopsy occurred at the National Defense Medical College Hospital. It consisted of 3 tuberculosis patients and 68 infected staff members over a 6-year observation period from 1997 to 2002 after exposure to an index patient. We report the incident and the background of the tuberculosis infection in our hospital. A 72-year-old man with myelodysplastic syndrome was admitted to our hospital and later died. Miliary tuberculosis was diagnosed at autopsy. The first non-periodic health examination was performed on the hospital staff who had contact with the patient. Tuberculosis infection was defined as an area of erythema not less than 30 mm in diameter in the tuberculin skin test. 13 of the 39 hospital staff members who had had contact with the patient were infected, and 3 developed tuberculosis. Of the latter 3 secondary tuberculosis patients, the only contact point two had had with the index case was in the autopsy room, and the other had had contact both in the autopsy room and on the ward. The incidence of tuberculosis infection among the staff who had had contact in the autopsy room alone was higher than among the staff who had had contact on the ward alone (odds ratio = 5.04; 1.08-23.42: 95% confidence interval). Because one of the secondary tuberculosis patients had bronchial tuberculosis, which is a strong source of infection, the second non-periodic health examination was performed on the staff who had had contact with the secondary tuberculosis patient, and 69 inpatients who had had contact with the staff were carefully observed over a two-year period. 58 of the 171 staff members were infected, and none developed tuberculosis. However, 23 patients were diagnosed with active tuberculosis after admission to our hospital during the 6 years from 1997 to 2002. Many of them were elderly patients with underlying diseases. An autopsy was performed on 6 of those who died, but only one was diagnosed with active tuberculosis before death. Five of the six autopsied patients had old, healed tuberculous lesions. This outbreak underlines the need for standard precautions, including anti-air droplet infection at autopsy, because antemortem diagnosis of tuberculosis is not always possible, and there is a risk of elderly hospitalized patients developing tuberculosis if they have been previously infected with Mycobacterium tuberculosis.