MOLECULAR EPIDEMIOLOGY OF TUBERCULOSIS IN DENMARK IN 1992

The incidence of tuberculosis (TB) is increasing all over the world, i ncluding in countries with a high standard of living and good social s ecurity, Denmark represents such a region, Furthermore, it is a small country (5 million inhabitants) with a long tradition in TB control, i ncluding a centralization of the bacteriological diagnostic facility, The present study was intended to analyze the transmission of Mycobact erium tuberculosis in a country in which TB has low endemicity by a co mbination of conventional epidemiological approaches and DNA fingerpri nting techniques, whereby individual bacterial strains can be traced, M. tuberculosis isolates from 92% of all new cases of bacteriologicall y verified TB in Denmark during 1992 were subjected to IS6110 DNA fing erprinting to visualize the DNA restriction fragment length polymorphi sm (RFLP) patterns of the isolated strains, The data obtained from the RFLP analyses were interpreted by using demographic data, such as age , sex, ethnicity, and residence, for the patients, The risk factors am ong the patients for being part of an active chain of transmission, as opposed to demonstrating reactivation of a previously acquired latent infection, were estimated by statistical analyses. The magnitude of T B transmission in 1992 in Denmark was determined, and transmitted infe ctions were shown to comprise at least one quarter of the total number of cases, Almost half of the TB cases involved patients of foreign or igin, However, most of these isolates showed unique DNA fingerprint pa tterns and were rarely part of an active chain of transmission, The ma jor chains of recent transmission were localized to distinct geographi cal regions in the country, TB is frequent among immigrants, especiall y from Asia and Africa, but it is apparently readily suspected, diagno sed, and treated by the health care system, Danish patients with pulmo nary symptoms are not primarily suspected to have TB and, therefore, p lay an important role in recent TB transmission in Denmark.