HIV-associated tuberculosis in developing countries: epidemiology and strategies for prevention

The association between tuberculosis and HIV presents an immediate and grave public health and socioeconomic threat, particularly in the developing world. In early 1992 WHO estimated that approximately 4 million people had been infected with both Mycobacterium tuberculosis and HIV since the beginning of the pandemic; 95% of them were in developing countries. The association between tuberculosis and HIV is evident from the high incidence of tuberculosis, estimated at 5-8% per year, among HIV-infected persons, the high HIV seroprevalence among patients with tuberculosis, the high occurrence of tuberculosis among AIDS patients, and the coincidence of increased tuberculosis notifications with the spreading of the HIV epidemic in several African countries. The impact of the two epidemics on resource-poor countries has ominous social and medical implications, and the already overstretched health services now have to face a tremendously increasing tuberculosis problem. HIV infection worsens the tuberculosis situation by increasing reactivation of latent tuberculosis infection in dually infected persons as well as by favouring rapid progression of new infections in the HIV-infected. This also results in an increase of the risk of infection and a subsequent increase of cases in the general population. In order to respond to this urgent problem, the highest priority must be given to strengthening tuberculosis control programmes in the countries where they are poorly developed and where the prevalence of HIV and tuberculosis infections is high. Besides improving the cure rate by early diagnosis and prompt treatment of patients with tuberculosis, two major strategies that need consideration include BCG vaccination and preventive chemotherapy among HIV-infected individuals. The latter strategy is considered as the most critical intervention that would help to limit the expected increase in clinical tuberculosis from the pool of HIV and tuberculosis coinfected individuals. However, a number of issues need to be addressed urgently and before such an intervention can be implemented in the developing countries.