The Spatial Diffusion of Human Immunodeficiency Virus Type 1 in Finland, 1982–1997

Abstract

Finland is one of the few countries in the world where every person found to be HIV-1 positive (suffering from any symptoms or not) is reported to the National Board of Health. This reporting and the wealth of census-based, detailed socioeconomic data available provide an excellent opportunity for the spatial analyses of the epidemic at a national level. It also provides the opportunity to create a model that considers risk factors for the population as a whole. Such a model also becomes important as the HIV-1 epidemic moves increasingly into the heterosexual population. The development of the HIV-1 epidemic in Finland, 1982–88, is first analyzed geographically using standard statistical methods. Then the growth of the HIV-1-positive population is predicted using two curves widely adopted in population dynamics, the logistic curve and the Gompertz curve. Finally, the spatial diffusion of HIV-1 in Finland, 1989–97, is predicted by applying the potential model and a simulation technique. Significant risk factors for the population as a whole include urban lifestyle, travel patterns and known risk behavior. The results suggest that the epidemic, in its initial stage in Finland, follows a hierarchical pattern demonstrated elsewhere. The simulation procedure also suggests that there is potential for an increase, in the near future, in the incidence of cases reported in hospital districts peripheral to the metropolitan region. Also expansion diffusion will begin to occur close to the epicenter. The results highlight the need for detailed data concerning the prevalence of HIV-1 and various socio-economic variables on a spatial basis and the need for more detailed geographical analyses and modeling of the ever-growing pandemic.

Key Words:

• spatial diffusion
• epidemics
• HIV
• AIDS
• modeling
• Finland