Is the AIDS incubation time changing? A back-calculation approach

Including pre-AIDS mortality in back-calculation model to estimate HIV prevalence in France, 2000

Since the advent of highly active antiretroviral therapy (HAART) the lengthening of AIDS incubation time has led to a decrease of AIDS incidence and mortality, and to the increase of the proportion of pre-AIDS mortality. The objective was to develop an extension of the back-calculation model by including pre-AIDS mortality and to estimate HIV prevalence in France. Our previous back-calculation model was modified to take into account the probability of survival for HIV-infected individual using the relative risk to die at different period for an HIV-infected person versus the general population (psi). AIDS cases reported to InVS (Institut de Veille Sanitaire) until March 2003 were back-calculated to estimate HIV incidence until December 2000. AIDS deaths occurring until December 2000 were used to obtain HIV prevalence in 2000. Plausible intervals were calculated taking into account uncertainties on AIDS incubation time. Taking into account pre-AIDS mortality increased the goodness-of-fit of the model to the data. The relative risk, psi, was estimated as 3 for homo-bisexual men, haemophiliacs and transfused cases, 10 for intravenous drug users, and 4 for heterosexual cases, with no difference over period. HIV prevalence in 2000 was estimated as 88,200 (with a plausible interval of 52,300-168,000), versus 78,200 when mortality was not considered. Pre-AIDS mortality estimates show the amount of this mortality during the era of HAART but also evidenced its existence before HAART. Taking into account pre-AIDS mortality of HIV-infected person in the back-calculation model increased the estimated HIV prevalence.

Comparing the public health burden of chronic hepatitis C and HIV infection in France

BACKGROUND/AIMS

In France, the prevalence of hepatitis C virus (HCV) exceeds that of HIV, but in the absence of treatment, HIV infection progresses more rapidly than HCV. More HIV-infected patients, however, have received treatment. Using reported public health data in France and natural history models, we applied the back-calculation method to project future mortality from HCV and HIV incorporating current therapies.

METHODS

The HCV model was based on literature data for the natural history of HCV and reports of hepatocellular carcinoma mortality. The HIV model used estimates from the French Hospital Database on HIV and reported AIDS cases and deaths.

RESULTS

Peak annual mortality from HIV at 5000 occurred in 1994 and was 1000 in 1998, but HCV mortality likely increased through the 1990s and reached 3000 in 1998. Considering only HCV infections occurring until 1998 and currently available therapy, our model suggested that annual HCV-related mortality would continue to rise and would reach 4500 deaths in 2022. In contrast, AIDS-related deaths began to decrease in 1997.

CONCLUSIONS

The public health burden of HCV is likely on the rise, while the burden of HIV, given the fairly widespread use of effective medications, may be on the decline. These results may help health policymakers in planning their responses to these epidemics.