Epizootological, serological, and molecular virological analysis of an outbreak of hemorrhagic fever with renal syndrome (HFRS) in the Egoryevsk district of Moscow region (September 1995-January 1996) has been carried out. Hantavirus (Puumala) antigen and virus-specific antibodies were isolated from bank voles captured in the endemic focus. Anti-Puumala antibodies were detected in the sera of all HFRS patients and in 2% healthy residents of the endemic focus. Analysis of nucleotide sequence (RNA from hantavirus-positive lung of a bank vole) showed that the studied hantavirus is a distinct genotype of Puumala virus. Hence, a new highly active natural focus of HFRS associated with Puumala virus, dangerous for the population, has been revealed in Moscow region.

Lung specimens of 1514 small mammals of 35 species captured in 1991-1995 at 9 territories of Russia were tested in ELISA for virus antigens of hemorrhagic fever with the renal syndrome (HFRS). The antigens were detected in lung specimens of Clethrionomys glareolus, Microtus arvalis, Microtus gregalis, Microtus fortis, Arvicola terrestris, Apodemus agrarius, Micromys minutus, and Sorex sp., well known as Hantavirus reservoirs, captured in the Vologda, Yaroslavl, Saratov, Astrakhan, and Chita regions. Infection of Microtus maximoviczii revealed in the Chita region was first found in China. Previously there were no reports about the circulation of hantaviruses in this region. Our study added one more host to the list of HFRS virus hosts: Meliones tamariscinus.

A new approach has been developed to evaluate the adequacy of HFRS clinical diagnosis, by using regression analysis of large selections. The HFRS morbidity rate and the antibody prevalence rate in man were viewed as a function and an argument of the function, respectively. An empiric model for one of the active HFRS endemic area (Saratov Province), characterizing the correlation between the immunity and morbidity rates has been elaborated. It calculates the theoretical morbidity level that corresponds to determine an immune portion of the population in each administrative area. The theoretical (counted) values were compared to the annually registered morbidity rates; their similarity has been estimated. Estimation of the adequacy of HFRS diagnosis in the examined region could have been admitted as satisfactory. However, various faults in the clinical identification of HFRS cases were found to occur in 14 of 44 districts of this region. Hyperdiagnosis was made in the most active HFRS natural foci (broad-leaved forests), but in the endemic areas being characterizes by moderate or low activity (forest-steppe and steppe districts). The results of the authors' calculations were shown to be generally in agreement with the data from the Regional Epidemiological Service reports which confirmed the adequacy of the proposed material.

Using large selections the unified system of landscape districting of HFRS natural foci with allocation of special geo-botanical provinces has been developed. This permits to avoid various deviations were found to appear during association of epizootiological and epidemiological indexes of separate towns and rural districts when estimating regional parameters. Adequacy of the offered system in confirmed by five-fold increase of the correlation between HFRS epizootiological parameters and antibody prevalence rate in humans. The steady maximum of all parameters was registered in the province situated in broad-leafed oak-line forests. Minimal values are found to correspond to one located in forest-steppe (with birch and asp forests) which poor fodder potential for rodents is well known. Other provinces between these ones are characterized by consecutive decrease of all index values according to the landscape type. According to estimated natural activity rate all the provinces are divided to three groups. The first one (antibody prevalence rate is above 5%) unites the high activity HFRS natural foci. Their common geographical location is on the territories with highest rodent population rates. The second group (antibody prevalence rate--2-4%) includes HFRS foci with average activity, and the third one (antibody prevalence rate is below 2%)--with low activity. The most of the last group provinces are situated on periphery or behind the bank vole living area.

Results of serologic screening of small mammals for antigen of the virus of hemorrhagic fever with the renal syndrome (HFRS) and of testing human sera for antibodies to this virus in Moldova are reviewed. A total of 9946 animals belonging to 22 species and blood sera of 792 healthy donors were examined in 1983-1990. HFRS virus antigen was detected in 30 animals of 9 species, with the highest incidence of the antigen in gray voles. Two serotypes of Hantavirus were found to circulate in small mammals: Puumala and Hantaan. Screening of healthy humans revealed antibodies to HFRS virus in 7.8%. Natural foci of HFRS were detected in 23 of the 44 administrative territories of the Republic situated in 5 landscape geographical provinces.

The incidence and antibody prevalence of hemorrhagic fever with renal syndrome (HFRS) in Bashkirtostan (European part of Russia) and northern Sweden was compared with the abundance of Clethrionomys glareolus (bank voles) in the two areas. In Bashkirtostan, 10% of the women and 15% of the men were found to be antibody positive. The corresponding figures for Sweden were 8% and 16% for women and men, respectively. The annual incidence of HFRS in Bashkirtostan was 50 cases per 100,000 inhabitants, with a male:female ratio of 4.6:1. The incidence in the endemic area of Sweden was seven cases per 100,000 inhabitants, with a male:female ratio of 1.8:1. A similar age distribution of cases, with a peak in the middle age groups, especially in men, was found in both Bashkirtostan and Sweden. The incidence of HFRS in humans and the abundance of bank voles varied with time in both Bashkirtostan and Sweden, but the study failed to find any significant correlation between the two variables. The study showed that HFRS causes significant human morbidity in the areas studied but that both incidence and possibly bank vole abundance was higher in Bashkirtostan than in northern Sweden.

For the first time the natural immune stratum to hemorrhagic fever with the renal syndrome (HFRS) among the population of all regions of Bashkiria, a large territory with the highest morbidity level in this infection in the USSR, was studied. 9,176 persons over 15 years of age were examined by radioimmune techniques. Analysis of the immune structure of the population revealed that the share of immune males was higher than that of immune females, but the difference was less than the difference between males and females among the registered HFRS patients. Among children immune persons were almost completely absent. The immune stratum increased rather slowly among persons under 40 years, and only from this age the considerable increase of the immune stratum was observed (up to 16.2 %). High risk groups included persons of such professions as forestry workers, truck and tractor drivers, oil workers and prospectors, livestock breeders, builders. These data may be used for the formation of groups to be vaccinated against HFRS in foci with different degrees of activity. Before vaccination the correction of groups to be vaccinated in a given region should be carried out, taking into account the immune structure of the population and the specific features of the local landscape and economy.

For the first time the natural immune stratum to hemorrhagic fever with the renal syndrome (HFRS) among the population of all regions of Bashkiria, a large territory with the highest morbidity level in this infection in the USSR, was studied. 9,176 persons over 15 years of age were examined by radioimmune techniques. Analysis of the immune structure of the population revealed that the share of immune males was higher than that of immune females, but the difference was less than the difference between males and females among the registered HFRS patients. Among children immune persons were almost completely absent. The immune stratum increased rather slowly among persons under 40 years, and only from this age the considerable increase of the immune stratum was observed (up to 16.2%). High risk groups included persons of such professions as forestry workers, truck and tractor drivers, oil workers and prospectors, livestock breeders, builders. These data may be used for the formation of groups to be vaccinated against HFRS in foci with different degrees of activity. Before vaccination the correction of groups to be vaccinated in a given region should be carried out, taking into account the immune structure of the population and the specific features of the local landscape and economy.