The bank vole (Clethrionomys glareolus) is the natural host of the Puumala virus (PUUV), an hantavirus endemic in Central and Northern Europe that cause a mild haemorrhagic fever with renal syndrome in humans. We studied the bank vole populations during five years at forest sites near households with confirmed repeated human infections and at forest areas chosen at random some distance away from the settlement. We found that voles where more abundant at the site near the human settlement compared to randomly chosen forest areas. We also found that voles with large body mass were more likely to have PUUV antibody reaction than smaller individuals irrespective of site and year of collection. We found that gut concentrations of nitrogen (N) of voles varied between sites but that N concentration of PUUV seropositive animals did not differ from the seronegative ones. Nitrogen concentration in the gut content did not vary between the sexes nor with body mass of animals. Age of animals were not important in relation to diet quality. A weak positive but statistically non-significant relationship between N in gut content and vole density was observed. The vole populations at the two areas showed direct density dependence and similar dynamic. On the other hand the seropositive cohort did not show a significant density regulation. One conclusion is that human disturbance of the environment near settlement may facilitate higher population densities of voles than at more undisturbed forest sites. It seems also that large animals living near human settlements are more likely candidates for transfer of the hantavirus within the vole population and to man.