The state of the art may have changed since the publication date. Subsequent studies, however, indicated that all INH-resistant strains should not be considered as being attenuated in their virulence to humans. Insertion sequences are suitable tools for the diagnosis and epidemiology of tuberculosis because of the highly variable copy number and variability of insertion sites in the chromosome. Patients with the same RFLP pattern constitute an epidemiologically linked cluster.
Clustering indicates recent infection and rapid progression to clinical illness.
Nearly one thirds of new cases of tuberculosis in San Francisco are the result of recent infection. In Thailand, tuberculosis has now emerged as the most common opportunistic disease associated with HIV infection. Ther have been numerous outbreaks of multidrug-resistant tuberculosis in the United States. Most of such outbreaks have primarily involved persons infected with HIV, who are thought to have been exposed to the strains in medical or correctional facilities. Always watch for outdated information.