Pogosta disease (PD), an epidemic rash-arthritis occurring in late summer is caused by Sindbis virus (SINV) and is transmitted to humans by mosquitoes. Altogether 2183 PD cases were serologically confirmed 1981-96 in Finland, with an annual incidence of 2.7/100000 (18 in the most endemic area of Northern Karelia). The annual average was 136 (varying from 1 to 1282) with epidemics occurring in August-September with a 7-year interval. Studies on 6320 patients with suspected rubella (1973-89) revealed 107 PD cases. The depth of snow cover and the temperature in May-July seemed to predict the number of cases. The morbidity was highest in 45- to 65-year-old females and lowest in children. Subclinical SINV infections were 17 times more common than the clinical ones. The SINV-antibody prevalence in fertile-age females was 0.6% in 1992; the estimated seroprevalence in Finland is about 2%. Among game animals the tetraonids (black grouse and capercaillie) had the highest seroprevalence (65%) in the epidemic year of 1981.

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Precise timing of natural and cultural events provides a foundation for understanding how past natural phenomena have driven changes in population and culture. In this study, we used high-resolution Bayesian chronology to describe an event sequence of a massive and abrupt water level decline of a large lake and the contemporaneous cultural changes that occurred in eastern Fennoscandia during the mid-Holocene. The study provides the first transdisciplinary analysis of the causes and effects of the events by using a combination of archaeological, geological and ecological data. Nearly 6000 years ago, ancient Lake Saimaa, estimated to cover nearly 9000 km2at the time, was abruptly discharged through a new outlet. The event created thousands of square kilometres of new residual wetlands. The archaeological record shows a profound cultural replacement and a subsequent sharp human population maximum in the area during the decades after the decline in water level. During the population maximum, the proportion of Alces alces (moose) in the diet rapidly increased and became prominent as a dietary resource. The eventual population decline in the area coincided with ecological development towards old boreal conifer forests, along with the colonization of a new species of tree Picea abies (Norway spruce). The new ecosystem was less suitable for moose to forage in, and this attenuated the dietary role of moose and thus contributed towards the eventual population and cultural decline. The methodological approach described in this paper allowed the reconstruction of past natural and cultural events and demonstrated how they can be causally intertwined.

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Exploitation by humans impacts wildlife in many ways. Selective harvesting regimes affect demography of the remaining population, and increased mortality shortens life expectancy affecting optimal life-history strategies. We studied this in a Finnish moose (Alces alces) population using harvest data on age, carcass weight, antler spread and tine number, and compared the growth in body weight and that of antlers in male moose after adult-biased and mixed age class harvesting. According to our results, both body weight and antler growth of young males increased after mixed age class harvesting. Changes in growth patterns were affected by population density and sex ratio, but as the period effect still remained in the growth patterns after removing the effects of density and sex ratio, we suggest that the change in male moose growth patterns might have resulted from the harvest-induced young-male age structure and higher harvest pressure among young male moose.