Objective: To estimate the frequency of acute retroviral syndrome associated with HIV infection among injecting drug users (IDU), and to determine the extent to which acute retroviral syndrome predicts a faster rate of progression to AIDS and immunosuppression in this population.
Design: Prospective study of HIV seroconverters (median follow-up, 50.5 months).
Setting: Sixteen clinical centres throughout Italy established to study the natural history of HIV infection.
Patients: Three hundred and ninety-one IDU for whom the date of HIV seroconversion was established with a 9-month precision.
Main outcome measures and methods: Incidence of acute retroviral syndrome with signs and symptoms that included fever (temperature > 38 degrees C) occurring within 6 months prior to the time of first positive HIV test, progression to AIDS, crude and adjusted relative hazard of AIDS using survival analysis techniques, and trajectories of CD4+ cell counts using a piece-wise linear regression model incorporating the degree of dependency of within-person measurements.
Results: Of 391 HIV seroconverters, 39 (10.0%) were diagnosed with acute retroviral syndrome. During follow-up, 13 seroconverters with acute retroviral syndrome and 24 asymptomatic seroconverters developed AIDS. The Kaplan-Meier estimates for the cumulative AIDS incidence during 4.5 years of follow-up were 26.8 and 6.5%, respectively; the relative hazard of developing AIDS for acute retroviral syndrome was 5.59 (95% confidence interval, 2.79-11.20) after adjustment for age, sex and year of seroconversion. Although CD4+ level within the first year from seroconversion was similar, the rate of CD4+ cell decline after 1 year from seroconversion was faster in individuals with acute retroviral syndrome than in those without this syndrome (P < 0.001).
Conclusions: Among HIV-infected IDU, a distinct acute retroviral syndrome is apparent and associated with a faster rate of clinical progression to AIDS and HIV-related immunosuppression.