Nosocomial tuberculosis in the AIDS era: strategies for interrupting transmission in developed countries

In developed countries where tuberculosis is increasing in association with HIV infection, nosocomial transmission among patients and from patients to health care workers is being increasingly reported. Nosocomial tuberculosis among HIV-infected patients is difficult to prevent by conventional control measures because the clinical presentation of the disease may be atypical and confused with other respiratory infections, because the tuberculin skin test is less reliable, because cough generating procedures may increase the probability of transmission, because HIV-infected patients may progress rapidly from infection to disease, and because the organisms are increasingly drug resistant, making preventive therapy difficult. Substandard ventilation and the recirculation of air in many contemporary buildings has also been implicated in widespread nosocomial transmission. Source control through isolation and effective treatment of known or suspected cases remains the most effective strategy for preventing transmission. Dilution of infectious droplet nuclei through ventilation with outside air is important, but incompletely protective. Like ventilation with outside air, filtration of recirculated air may reduce the chance of infection by dilution, but it is expensive. Traditional surgical masks offer the wearer little or no protection. Finally, ultraviolet air disinfection may augment ventilation by inactivating organisms in the upper room air, or in ventilation ducts.