Epidemic model of HIV infection and AIDS in Argentina. Status in 1990 and predictive estimates

The purpose of this paper was to evaluate the prevalence of HIV infection and AIDS in Argentina, to study the dynamics of the spread of HIV and to predict the future course by means of an epidemic model. The model was constructed using differential equations to describe the interactions between members of the various groups at risk. The functional form of the solutions was used in a back calculation procedure using data from cohort studies which were done in other countries (U.S.A. and France) together with data of AIDS cases reported to the National AIDS Program, to determine the time evolution of HIV-infection in each of the groups at risk defined. Results show that HIV was introduced in Argentina during the early 80's and affected persons of the homosexual/bisexual group in a first stage. In April 1990 it was estimated that there were a total of 34,131 HIV-infected persons. Intravenous drug users (IVDU) represented 39.5%, homosexual/bisexual men 47.6% and heterosexual adults 11%. It is estimated that in December 1992 there will be 107,946 HIV-infected persons where heterosexuals contribute with more than 20% of that value. AIDS cases predicted for the same period are 4130, with 1958 among homosexual/bisexual, 1483 among IVDU, 449 in heterosexual adults, 153 in children under 4 years old and 87 among hemophiliacs or patients with blood coagulation disorders. By the end of 1994 the model predicts more than 200,000 HIV infected persons with an important proportion of heterosexual adults and more than 12,000 AIDS cases. The values of this period must be considered as a future possible scenario if the present spread conditions are preserved. Infection among heterosexual adults is at the present time in a first and exponential phase of spread and dominated by transmission from IVDU group and bisexual men. It is concluded that the future course of AIDS epidemic in Argentina may be particularly influenced by changes in the heterosexual behavior particularly in those with a higher degree of exposure to HIV-infection.