Characterizing trends in HIV infection among men who have sex with men in Australia by birth cohorts: results from a modified back‐projection method

Handan Wand,Andrea Gonnermann,David Wilson,Matthew Law,Ping Yan,Ann Mcdonald,John Kaldor

doi:10.1186/1758-2652-12-19

Abstract

BackgroundWe set out to estimate historical trends in HIV incidence in Australian men who have sex with men with respect to age at infection and birth cohort.MethodsA modified back-projection technique is applied to data from the HIV/AIDS Surveillance System in Australia, including "newly diagnosed HIV infections", "newly acquired HIV infections" and "AIDS diagnoses", to estimate trends in HIV incidence over both calendar time and age at infection.ResultsOur results demonstrate that since 2000, there has been an increase in new HIV infections in Australian men who have sex with men across all age groups. The estimated mean age at infection increased from ~35 years in 2000 to ~37 years in 2007. When the epidemic peaked in the mid 1980s, the majority of the infections (56%) occurred among men aged 30 years and younger; 30% occurred in ages 31 to 40 years; and only ~14% of them were attributed to the group who were older than 40 years of age. In 2007, the proportion of infections occurring in persons 40 years or older doubled to 31% compared to the mid 1980s, while the proportion of infections attributed to the group younger than 30 years of age decreased to 36%.ConclusionThe distribution of HIV incidence for birth cohorts by infection year suggests that the HIV epidemic continues to affect older homosexual men as much as, if not more than, younger men. The results are useful for evaluating the impact of the epidemic across successive birth cohorts and study trends among the age groups most at risk.

Highlights

We set out to estimate historical trends in HIV incidence in Australian men who have sex with men with respect to age at infection and birth cohort
Similar approaches have been used to estimate age-specific historical trends in the past [4,5,6,7], but the methodology used in this study extends previous methods and makes maximal use of available HIV/AIDS data sources in Australia's surveillance databases, including "newly diagnosed HIV infections", "newly acquired HIV infections" and "AIDS diagnoses", to estimate trends in HIV incidence
In Australia, HIV transmission is monitored through the notification of cases of newly diagnosed HIV infection, including cases with evidence of newly acquired HIV infection

Summary

Introduction

We set out to estimate historical trends in HIV incidence in Australian men who have sex with men with respect to age at infection and birth cohort. Despite apparent successes in the past, the most current data [2] indicate an ~40% increase in new HIV diagnoses in 2007 from the year 2000 among Australian men who have sex with men (MSM). Since 1991, further surveillance has been supplemented by national notification of HIV diagnoses with evidence of newly acquired HIV infection, defined as new HIV diagnoses with either a previous negative HIV test within 12 months, or with evidence of a recent seroconversion illness. These data are indicative of trends in the HIV epidemic, they cannot be used directly to estimate HIV incidence (number of new infections per year).

Methods

Results

Conclusion