ESTIMATION OF THE IMPACT OF THE HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION ON TUBERCULOSIS - TUBERCULOSIS RISKS REVISITED

The human immunodeficiency virus (HIV) infection has both a direct and an indirect effect on the incidence of tuberculosis. The direct effec t is due to the increased number of cases among HIV-infected individua ls because of their enhanced susceptibility to the disease. The indire ct effect is increased transmission of Mycobacterium tuberculosis infe ction in a community with high levels of dual infection, as a conseque nce of infectious cases occurring in HIV-infected persons. The risk of infection by M. tuberculosis in the population will then increase, as will the number of tuberculosis cases in the general population. Acco rding to the World Health Organization, over 4 million people are esti mated to be dually infected with HIV and M. tuberculosis worldwide. In 1990, it was estimated that 300 000 new TB cases (4% of total new cas es) were attributable to HIV infection; around 1.4 million cases are e xpected per year by 2000 (equivalent to about 14% of expected cases), thus increasing the reservoir of tuberculosis patients capable of tran smitting the infection to others, and increasing the burden on the alr eady overstretched National Tuberculosis Control Programmes, especiall y in resource-poor countries. This paper is a review of methods sugges ted to quantify the effect of the interaction between HIV infection an d tuberculosis at population level, and more particularly the effect o f HIV on the risk of tuberculosis infection.