HIV outbreak among injecting drug users in the Helsinki region: social and geographical pockets

Background: Incidence of newly diagnosed HIV infections among injecting drug users (IDUs) in Helsinki rose from 0 per 100 000 inhabitants in 1997 to 2.9 in 1998 and to 11.1 in 1999. Thereafter incidence declined to 2.1 in 2003. Methods: Data were collected from interviews with HIV-positive IDUs who attended the University Hospital in Helsinki from 1998 until 2003. We studied the sociodemographic profile and spatial distribution of IDUs who were diagnosed in the beginning of the outbreak and those diagnosed later. The indicator for the spatial differentiation within the metropolitan area is % employed males aged 25–64. Results: The outbreak occurred among a marginalized population of IDUs characterized by a long history of injecting drug use (10.7 years), mean age 32 years, homelessness (66.3%), history of imprisonment (74.7%) and psychiatric hospital care (40.6%). Compared with 98 early cases diagnosed during the first 2 years until 2000, 47 recent cases diagnosed after 2001 were 4 years older, and as marginalized. Except for the city centre, both early and recent cases had been living or using drugs in the same deprived neighbourhoods with the highest unemployment rates. Up to 40% of cases in the two big geographical clusters did not have contact with the city centre, where the needle exchange services were available. Conclusions: The Finnish HIV outbreak is restricted socially to a very marginalized IDU population, and spatially to local pockets of poverty. In low prevalence countries, prevention programs should be targeted early at high-risk areas and populations.