Background:  Since 2001, Medecins sans Frontières (MSF) has provided free diagnosis and treatment of opportunistic infections and ART in resource-limited settings. We report the incidence of opportunistic infections in the 24 months after ART initiation in adults.

Methods:  We used routine data (FUCHIA software) from patients receiving ART between March 2001 and May 2006. We calculated the overall and disease-specific incidence of new episodes of WHO stage 3 and 4 opportunistic infections for 3 periods after ART initiation:  the first 3 months (T3), 3 to 6 months (T6), and 6 to 24 months (T24). Continent-specific incidence rates were also calculated. Follow-up was censored at the dates of the corresponding opportunistic infections diagnosis, death, or loss to follow-up.

Results:  After excluding 2122 patients not seen after ART initiation, 54,554 adults (96%) contributed 11,120 person-years of follow-up at T3, 9815 person-years at T6, and 28,118 person-years at T24. At ART initiation, patients’ median age was 35 years (IQR 29.5 to 41.4), median CD4 count 104 cells/mL (IQR 40 to 175; n = 38,017) and 14% had a body mass index <17/kg/m² (n = 39,717); 95% were ART-naïve and 95% were receiving cotrimoxazole prophylaxis (59% still after 6 months of ART). The overall incidence of opportunistic infections decreased from 74/100 person-years during T3, to 33/100 person-years during T6, and 16/100 person-years during T24. The most frequently recorded infections at T3, T6, and T24 were oral candidiasis, severe bacterial pneumonia, and pulmonary tuberculosis infection (see the table). The highest incidence of newly diagnosed Kaposi’s sarcoma was found in Africa and that of cryptococcosis, in Latin America. In these continents, rates decreased from 4.5/100 person-years during T3 to 0.7/100 person-years during T24 for Kaposi’s sarcoma, and from 6.4/100 person-years to 0.9/100 person-years for cryptococcosis.

Conclusions:  In resource-limited settings the burden of opportunistic infections in patients on ART decreases significantly with time on treatment. Nevertheless, incidence rates remain high and, therefore, reliable diagnostic tools and effective opportunistic infections treatment must be made available during the scaling-up of ART in such settings.