[Tuberculosis and the HIV pandemic. Risk of nosocomial tuberculosis infection]

Abstract

Spread of human immunodeficiency virus (HIV) infection has had a major impact on the epidemiology of tuberculosis. In several African countries the incidence of tuberculosis has doubled, and the prevalence of HIV infection among patients with tuberculosis is 20 to 60%. A similar change has occurred in some developed countries. Several factors, including HIV infection, have contributed to this change. Tuberculosis among HIV infected patients is probably more often a result of a new infection with Mycobacterium tuberculosis than reactivation of a latent infection. In the USA in particular several outbreaks of multidrug-resistant tuberculosis have been reported. The mortality among patients has been high, and there have been several cases of transmission to healthcare workers. Analyses of these recent outbreaks indicate that it is possible to intervene by well known prophylactic measures. Rapid diagnosis and treatment, and correct isolation procedures are essential to prevent outbreaks.

PIP: Approximately 4 million people are infected with tuberculosis (TB) in the world, of whom 3.5 million live in sub-Saharan Africa. The incidence of HIV infection among TB patients in several African countries ranges from 20% to 60%. During 1989-92 both American and European major cities reported an increasing number of TB cases among younger people. Studies from New York and San Francisco also revealed that 40% and 30% of newly registered TB cases, respectively, were attributed to new infections rather than the reactivation of latent infection. A study of 6546 patients diagnosed with AIDS during 1979-89 in Europe also found that 14% of them had TB at some time during the course of the disease, mainly in southern Europe and among drug users. Multidrug-resistant Mycobacterium tuberculosis (MDRTB), which is resistant to isoniazid and rifampicin, increased in the US from 0.5% to 3.5% during 1982-91, with 19% of all MTB isolates reported to be MDRTB in New York in April 1991. Among patients not treated earlier, the multidrug-resistant isolates were more frequent among HIV-positive than HIV-negative patients (16% vs. 3%). During 1990-92 there was also a number of nosocomial TB cases reported in the US. The outbreak affected about 200 patients, most of them HIV-positive, and the mortality rate was high (72-89%). In the US, at least 20 health care workers were infected with MDRTB, and 9 (7 of which HIV-positive) died. In a Michigan substance-abuse facility an AIDS patient with MDRTB transmitted the illness to 15 (21%) of 70 health care workers during a 5-week hospitalization. In a Florida hospital, 36% of health care workers were infected during a 2-year period in a unit with HIV-positive patients, whereas none were infected in a thoracic surgery division. The prevention of MDRTB transmission was accomplished by isolating the patients with MDRTB as well as by rapid diagnosis and treatment.