[Tuberculosis and HIV: two infections one problem (editorial)]

Several issues in the incidence diagnosis treatment and prevention of tuberculosis (TB) in the HIV seropositive population are discussed. About one-third of the worlds population harbors Mycobacterium tuberculosis or M. bovis. The World Health Organization estimates that ten million adults and one million children are HIV seropositive. Around four million including 300000 in Latin America have both infections. The average lifetime risk of developing active TB is 10% for an immunocompetent individual harboring the bacterium. At present coinfection with HIV is the greatest risk factor for TB. The proportion of TB patients who are HIV seropositive ranges from 20 to 66% in countries where both infections are significant. The proportion of AIDS patients with TB reflects the prevalence of TB infection in the general population. In sub-Saharan Africa the observed proportion ranges from 20 to 44%. In Argentina the incidence of TB in the general population has been declining about 7% annually but TB is the second most frequently encountered infection in AIDS patients. The incidence of TB is much greater among iv drug users who account for over 40% of the HIV seropositive population. TB is the only disorder associated with HIV that is transmissible to the general population. Infectivity of a TB patient results from elimination of bacteria in respiratory secretions and not from HIV. The basic TB control strategy is to detect infectious patients and treat the disease to decrease suffering and break the chain of transmission. Some atypical forms of TB in AIDS patients may be less infective than typical pulmonary cases producing positive tuberculin test reactions. Sputum examination for TB the simplest fastest and least expensive method of diagnosis is useful for coinfected patients although it has a higher false negative rate than in the general population. In general a laboratory using correct techniques can confirm TB diagnoses in a high proportion of cases. New methods are needed for cases negative on sputum examination and extrapulmonary and atypically presenting cases especially in countries with inadequate technical and economic resources. Chemoprophylaxis is effective in preventing active TB in coinfected persons. The main questions at present concern the most effective drug regimen and to whom it should be applied. Studies are underway to define the possible risk of BCG vaccine in newborns with high probability of perinatal HIV infection. The BCG vaccination policy should remain unchanged until studies are completed especially when the risk of TB infection is high.