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Sera of 3951 inhabitants of Central, Privolzhsky and Northwest federal districts of Russia were examined with the use of ELISA-IgG and neutralization test. Antibodies to West Nile virus (WN) were detected in the sera of residents of Voronezh (1,6% of cases), Tula (1,5%), Tambov (0,7%) and Lipetsk(0,6%) regions. Two positive samples have been detected in residents of Moscow and Moscow region, which were possibly infected, during theirs travel to endemic for WN fever regions. All sera obtained from Kaluga, Ryazan, Tver, Vologda, Ulyanovsk regions and The Republic of Tatarstan were negative. Our data, in combination with the morbidity rate of WN fever indicate on epidemiological activity of foci of this infection in the South, the North Caucasus, Privolzhsky (Saratovskaya region) and Central (the forest-steppe zone and Tula region) districts. The northern border of circulation of WN virus probably dispose of the latitude of the Tula region.

For the period from 2001 to 2011 zoological and epizootological studies in more than 100 points of Northwestern Caucasus including territories of Krasnodar Region and Republic of Adygea were carried out. 8723 specimens of small mammals represented by 20 rodent species and 7 insectivorous species were captured and examined. Organs and blood from 5057 specimens of creatures were studied for hantavirus infection. The presence of natural foci of circulation of 2 species of hantavirus--Dobrava/Belgrade and Tula--was established. Sochi viruses and presumably Kurkin with main natural hosts--Caucasian wood and field mice belong to the first species. Tula and Adler viruses with the main host--Microtus genus vole belong to the second species. Quantitative characteristics of infection of small mammals of various species during different seasons and years on the examined territories were obtained, that allowed to create a map of allocation of foci of hantavirus circulation that differ by structure.

From 2000 to 2011 85 600 cases of hemorrhagic fever with renal syndrome (HFRS) were registered in Russian Federation. Epidemically active foci of HFRS infection are located generally in temperate latitudes of the European part and the Far East. In the Far East regions whose fraction of all the HFRS disease cases in Russia is around 2%, the causative agents of the infection are Hantaan, Amur, Seoul hantaviruses, the natural reservoir for those are striped field mouse, Korean field mouse and brown rat. In the European part of Russia the causative agent of the infection are Puumala hantavirus as well as 2 genetic subtypes of Dobrava virus, the main reservoirs of those in the nature are bank vole, striped field mouse and Black Sea field mouse, respectively. 9 strain of Puumala and 10 strains of Dobrava virus were isolated. Based on sequencing of Dobrava virus strains significant differences were detected between Dobrava virus strains isolated from Black Sea field mouse from Sochi and striped field mouse from Lipetsk Region. Cultural inactivated vaccine against HFRS was developed and completed preclinical trials.

The findings suggest that there are natural foci of hantavirus infection in the Tambov Region. There is evidence that Dobrava/Belgrade hantavirus (DOB-Aa) was a leading etiological agent in the outbreak of the disease in the winter of 2006-2007. Epidemiological analysis showed that the outbreak of hemorrhagic fever with renal syndrome (HFRS) afflicted the region during November to April, by reaching its peak in January (52.2%). Among the patients with HFRS, rural dwellers were 91%. People were infected with the virus mainly by taking care of domestic animals (97.2%). The reservoir of the virus and the source of its human infection in the outbreak was a field mouse, its western subspecies Apodemus agrarius agrarius, which was absolutely dominated among all the virus carriers.

Twenty-six patients with hemorrhagic fever with renal syndrome (HFRS) were revealed as a result of serological examination of 582 patients with fever living around Sochi town. Etiologic role of Dobrava virus subtype as the cause of HFRS was assessed by immunofluorescent and ELISA assays, and neutralization test. The principal host of this virus and source of infection for humans is Caucasian forest mouse Apodemus ponticus. HFRS morbidity was sporadic and not dependent from patients' occupation and season. Comparative analysis of clinical and laboratory data from HFRS cases caused by DOB/Sochi and DOB/Lipetsk subspecies, as well as Puumala virus showed higher proportion of severe forms of disease in patients with HFRS from Sochi.

The authors of the article describe two cases of hemorrhagic fever with renal syndrome (HFRS) with prevalence of signs of nervous system involvement. The first case was a 40-year-old woman with moderate HFRS, who developed Guillain-Barre syndrome of axonal-demyelinating polyneuropathy. An important observation was the absence of hemorrhagic or renal syndrome; combined therapy including plasmapheresis was successful. The second case demonstrated polymorphism of HFRS clinical manifestations with prevalence of neurological symptoms, which consisted in encephalopathy and no renal failure signs; hemorrhagic syndrome was moderate. In both cases the diagnosis was confirmed by elevated titer of antibodies to HFRS virus, belonging to the group of hantaviruses.

A natural focus of hantavirus infection was detected and examined during the studies conducted in 2000-2002 around the Sochi (the western spurs of the Great Caucasus Ridge, which descended to the Black Sea (the Krasnodar Territory of Russia). At least 4 rodent species, such as Microtus majori, A. (S.) ponticus, A. agrarius, A. (S.) ciscaucasicus, were shown to participate in the circulation of hantaviruses. A comparative analysis of the nucleotide sequences of genomic S- and M-segments of hantaviruses has provided evidence that 13 viral RNA isolates from the A. (S.) ciscaucasicus belong to the Dobrava/Belgrade virus clade; however the RNA isolate from the Microtus majori belong to the Tula virus clade.

As a result of virological studies, 185 lung tissue specimens from 4 rodent species caught near Khabarovsk were isolated and fixed in the passages of cultured Vero-6 cells of 68 hantavirus strains. The capacity of the strains to adapt to the cells was assessed by using the adaptive index involving the mean rates of successful isolation, its duration, hantavirus antigen titer in the material used for infection. The strains of hantavirus serotypes were noted for the highest adaptive properties, which are ecologically associated with rodents of the family Mus, such as field and East-Asiatic mice. Lower adaptive capacities were established for the strains of hantavirus serotypes, which are ecologically related to rodents of the family Cricetidae, such as large and large-toothed redback voles. The differences found in the adaptive capacities of hantavirus strains cultured in Vero-E6 cells reflect the degree of specialization of some hantavirus serotypes to particular host rodent species during their long-term coevolution.

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.

The outbreak of hemorrhagic fever with renal syndrome (HFRS) in the Republic of Bashkortostan, resulting in 10,057 registered cases of the disease (287 cases per 100,000 of the population), was analyzed. HFRS cases among the population were registered in 52 out of 54 regions of Bashkortostan. 31% of the total number of patients were the inhabitants of rural regions (170 cases per 100,000) and 69% were urban dwellers (295 cases per 100,000), mainly in Ufa (512 cases per 100,000). HFRS morbidity among males was fourfold higher than among females. In 70% of cases persons aged 20-49 years were affected. 5% of the total number of patients were children aged up to 14 years. In 34 cases (0.4%) the severe clinical course of the disease had a fatal outcome. Cases of HFRS were registered from April 1997 till March 1998 with the highest morbidity rate observed during the period of August-December. In most cases (46.8%) both urban and rural dwellers contacted infection during a short-term stay in the forest. As the result of the serological examination of the patients, all HFRS cases were etiologically attributed to hantavirus, serotype Puumala. The main natural reservoir of this virus and the source of human infection in Bashkortostan were bank voles (Clethrionomys glareolus), the domination species among small mammals in this region.

Enzyme immunoassay with biotin-labeled monoclonal antibodies to Puumala virus was used for typing hantavirus antigens. The system is type-specific, that is, it detects Puumala virus only, which was demonstrated by typing 9 hantavirus antigens in infected Vero E5 cells and by epizootological analysis of an HFRS outbreak in the Yegoryevsk district of the Moscow region in November-December 1995. The suggested system may be used as an element of EIA screening of natural samples in analysis of the screening results.

85 hantavirus (HV) strains from Russia and other counties were examined by indirect fluorescent antibody test using monoclonal antibodies (MAbs) prepared against hantaviruses: Hantaan (Hantaan 76-118, A-9 strains), Seoul (SR-1, R-22 strains) and Puumala (Hallnas 83-223 strain). 68 HV strains were differentiated into five virus type groups: Hantaan, Puumala, Seoul, Prospect Hill and Belgrade-Dobrava. 17 strains were found to be antigenically closely related but distinct from Hantaan type (4 strains), Puumala (6 strains) and Prospect Hill (7 strains). The antigenic characteristics of these 17 strains suggested two supplementary antigenic subgroups of the Hantaan, two of Puumala and two of Prospect Hill.

Genus-specific monoclonal antibodies to nucleocapsid protein of Pumala virus and polymerase chain reaction were used to assess the specificity of a previously described polyclonal (based on human IgG to Pumala hantavirus) enzyme immunoassay (EIA) system for detecting hantavirus antigens. Parallel testing of crude lung suspensions from wild rodents trapped in different regions of Russia for hantavirus antigens and RNA showed 100% coincidence of the results of three tests. These data indicate a high specificity of polyclonal EIA system and its efficacy for screening of natural samples.

Thirty-two hantavirus strains and 8 samples of lung tissue from rodents collected in different regions of Russia have been examined by molecular biological methods. Two methodological approaches have been employed for the study of genetic relationships between the viruses: nested PCR assay and common RT-PCR with subsequent direct sequencing of 200 and 365 base pair of G2 protein encoding regions of M-segment, respectively, and the resultant sequences were compared with those of the prototype hantavirus. The study revealed a mosaic pattern of distribution of different hantavirus genotypes on the territory of Russia.

A sensitive micro EIA utilizing antigen or antibody dotted onto nitrocellulose filters (Dot-ELISA, Dot-blot) has been developed for laboratory diagnosis of hemorrhagic fever with the renal syndrome (HFRS) by detecting the virus specific IgM and IgG in the sera of HFRS patients and the antigen in crude lung suspensions of wild rodents. Measurements of specific IgM and IgG in paired HFRS sera collected during the first month of the disease showed clear-cut seroconversion and 100% correlation with the results of immunofluorescent test. The results of antigen detection in lung suspensions of 605 wild rodents trapped in various regions of Russia were identical to standard ELISA results. This rapid and inexpensive test may be useful in early serologic diagnosis of HFRS and in field serological and epizootological studies.

By indirect immunofluorescence using antigens of hantavirus Hantaan and CG 18-20 on Vero E6 cells were examined 5,827 samples of sera from 5,299 probands of Czechoslovakia. In 49 persons (0.94%) were found antibodies of titres 1:32 and higher. Two groups of elderly farm workers showed a cluster of positive individuals amounting to 9.9% and 29.4% respectively. The ratio of positivities in some other, randomly and specifically selected groups was deep below 1%. The partial results for the group of farmers were confirmed by RIA test. Occasionally antibodies only to one of the hantavirus serotypes, at other time, to both were found. The authors discuss the findings of antibodies of the two serotypes in humans as related to the evidenced existence of two hantavirus antigen serotypes in animals.

Studies on serodifferentiation by indirect immunofluorescence antibody method and neutralization test of Hantaan virus strains isolated from human patients and rodents revealed circulation on the Maritime Territory of 5 virus serotypes and demonstrated that rodents of one species could be virus carriers of different virus serotypes. On the basis of the antigenic similarity of strains isolated from human patients, field mice, and Clethrionomys rufocanus it is concluded that the virus serotypes circulating among rodents of these species may play a role in the etiology of cases of hemorrhagic fever with renal syndrome.

Virus-specific proteins G1, G2, and N with molecular weights of 70, 55-57, and 50 kilodaltons, respectively, were detected by radioimmunodiffusion tests in VERO E-6 cells infected with strains of virus of hemorrhagic fever with renal syndrome (HFRS) isolated in the European USSR from a patient with HFRS, a fatal human case of HFRS (the strains K-27 and P-360) and from a bank vole (strain CG-1820). The sera from human convalescents after HFRS in the European USSR and rat sera prepared with the CG-1820 strain precipitated proteins possessing similar electrophoretic characteristics from a lysate of cells infected with the CG-1820, K-27 and P-360 strains. The sera from human HFRS convalescents in the Far East did not precipitate protein Gl. The viral RNA derived by immunosorption method from intracellular nucleocapsids of CG-1820 strain and strain 4590 (isolated from Ap. Peninsulae in the Far East) contained 3 classes of molecules: L, M, and S. L- and M-RNA of these strains had the same molecular weight (1.62 and 1.38 megadaltons). The molecular weight of S-RNA of the strain 4590 was 0.76 megadalton and that of the CG-1820 strain 0.83 megadalton. It is assumed that there are species differences among the viruses, causative agents of HFRS, circulating in the European and Far East regions of the USSR.

The radioimmunoassay of serum samples from 76 convalescents after hemorrhagic fever with the renal syndrome (HFRS), that took place in 1964 in Ufa, revealed the presence of specific antibodies in 75% of the convalescents. The absence of antibodies may be attributed both to their loss in some of the convalescents and to mistakes in the clinical diagnosis. The study of serum samples from 19 convalescents who had the infection in 1960 during the laboratory outbreak of HFRS at the Gamaleya Institute of Epidemiology and Microbiology (Moscow) showed the presence of antibodies in all convalescents. In both groups the infection was linked with common red-backed voles (the Western serological variant of the virus).

Natural immunity to hemorrhagic fever with the renal syndrome (HFRS) in the human population of the Bashkir ASSR having the highest incidence of this infection was first studied using radioimmunoassay. The antigen was a suspension of lungs of rodents from natural foci containing high antigen titres. When 1726 human sera from 8 districts and 2 towns were examined, antibodies to HFRS were found in 20.1%, with variations from 6.9% to 41.5% in different territories. No relationship between the percentage of immune subjects and average incidence values for 17 years was found. In the immune population, men accounted for 21.3%, women for 19.3%. Among subjects under 40, the immune stratum was lower (17.5%) than among older subjects (26.2%). The percentage of immunity was found to depend on the occupation of the population. No significant difference in immunity could be found in persons with different blood groups. Antibody in HFRS convalescent was shown to persist in high titres for up to 20 years after the onset of the disease.

The necessary conditions of solid-phase radioimmunoassay (SPRIA) have been developed for the detection of arenavirus antigens (Junin, Machupo, Tacaribe, Amapari, and LCM). The sensitivity of SPRIA is higher than that of the complement fixation test more than 100-fold. The antigens could be detected by this method in various materials.

The evidence of the existence of natural foci of HFRS in Penza region has first been presented on the basis of serological examinations of patients and normal population as well as HFRS virus antigen demonstration in the lung tissue of small mammals. An outbreak of HFRS among children in a pioneer camp is described. Aerogenic infection of the children contracted from HFRS virus-infected bank voles (Clethrionomys glareolus) living near the camp is assumed. The detection of HFRS antigen in 5 species of small mammals indicates the polyhostal nature of HFRS foci existing in the region.

Four strains of hemorrhagic fever with renal syndrome (HFRS) virus were isolated from the lungs of Cl. glareolus caught in natural foci of HFRS in the European USSR. Preliminary experiments using enzyme-immunoassay (EIA) established the appurtenance of HFRS antigen in lung suspensions to the "western" serotype. Four strains were isolated in Vero-E6 cell culture after several blind passages and identified as the "western" serotype of HFRS virus. One stram originally isolated in Wistar rats and passaged in them 4 times and then adapted to Vero-E6 cells showed a closer antigenic relationship with the "eastern" HFRS virus serotype.

The circulation of the causative agent of hemorrhagic fever with renal syndrome (HFRS) in Georgia was studied. Altogether, 7,938 small mammals of 16 species trapped in 23 administrative areas of the republic were examined, and the specific antigen of HFRS virus was detected in 308 (3.8%). In serological examinations of 10 patients, antibody to HFRS virus was found in 4. Analysis of the above results indicates the existence of natural foci of HFRS in the Georgian SSR.

The virus of hemorrhagic fever with renal syndrome serologically similar to Hantaan virus was isolated from three rodent species, Ap. peninsulae, Cl. rutilus, Cl. rufocanus, and from human patients in Vero E6 cell culture.

Clinical serological studies of hemorrhagic fever with renal syndrome (HFRS) demonstrated high effectiveness of indirect immunofluorescence procedure (IF) for serodiagnosis of this infection. The use of HFRS virus-infected VERO-E6 cells as the antigen for IF enhanced the sensitivity and specificity of the method as compared with the use of cryostatic sections of the lung tissue from wild rodents spontaneously infected with HFRS virus as the antigen. A technology for preparation of a polyvalent HFRS diagnosticum containing the antigens of two virus serotypes has been developed for serological diagnosis of HFRS in the European foci where the serological evidence of circulation of strains of serotypes 1 and 2 of HFRS virus pathogenic for man has been obtained. The specificity and sensitivity of detection of antibody to HFRS virus serotypes 1 and 2 by IF test using the polyvalent diagnosticum is equal to that in tests using individually tissue culture antigens of HFRS virus serotypes 1 and 2. It was found that in the patients' native sera antibodies of the IgM class are masked by antibodies of the IgG fraction, therefore the use of IF technique for detection of IgM antibody to HFRS virus aimed at early serological diagnosis of this infection is not effective.

Conditions have first been developed for the preparation of erythrocyte immunoglobulin diagnostic preparation of erythrocyte immunoglobulin diagnostic preparation for HFRS virus which permits express detection of the specific virus antigen in suspensions of the lung tissue of rodents by means of the indirect hemagglutination test (IHA) and laboratory diagnosis of the infection in humans by means of antibody detection by the indirect hemagglutination-inhibition test (IHAI). The IHA test is as sensitive as immunofluorescence, while the sensitivity of the IHAI test is not inferior to that of immunofluorescence but is higher than that of RIA.

Certain features of humoral immunity in patients suffering from hemorrhagic fever with renal syndrome (HFRS) in the territory of the European USSR were established: a trend for increasing antibody levels for a long time after convalescence (approximately 6 months) and the lack of significant decline of antibody levels for many years (5-10). Comparative clinico-serological studies revealed the occurrence of subclinical and atypical forms of HFRS disease.

Indirect enzyme-linked immunosorbent assay (ELISA) and solid-phase radioimmunoassay (SPRIA) using either anti-human or anti-mouse IgG labelled with horseradish peroxidase and 125I, respectively, were developed for the detection of Junin, Machupo, Tacaribe, Amapari, Tamiami, Lassa and LCM arena-viruses. Both methods allow high sensitivity detection of arena-virus antigens and antibodies.

Natural foci of hemorrhagic fever with the renal syndrome (HFRS) have been found for the first time in the Komi ASSR. The main source of the causative agent in this territory was Clethrionomys glareolus the average infection rate of which was 4.4% and in some areas as high as 22.6%. For the first time in the republic the portion of human population naturally immune to HFRS was determined, comprising 5.2% of the population. The immune structure of the population did not differ from that in other focal territories of the European part of the USSR.

A direct ELISA technique was used for demonstration of HFRS virus antigen in suspensions of the lungs obtained from 774 wild small mammals belonging to 13 zoological species trapped in 21 localities in Czechoslovakia between 1983 and 1984. Western serotype of HFRS virus was demonstrated in the lungs of 8 Microtus arvalis voles caught in the areas of central Bohemia, southern Moravia and western Slovakia, and in one Clethrionomys glareolus vole from the area of eastern Slovakia. The eastern serotype antigen was found in one Apodemus agrarius field mouse captured in the area of eastern Slovakia. The antigen titres as determined in the lungs of these rodents by the ELISA and RIA techniques were relatively high. Human sera examined for the presence of HFRS-specific antibody by the indirect fluorescence and RIA techniques were 76 serum specimens from chronic kidney patients treated by hemodialysis and 349 sera of adult males over 35 years of age coming from various districts of Bohemia and Moravia. Antibodies against HFRS virus antigen were found in 4 sera obtained from northern Bohemian men. The results provide the evidence which suggests that the natural foci of HFRS are likely to occur across much of the Czechoslovak territory, and confirms the focality of this infection in at least some of the localities characteristic in the 1950s and 1960s of the incidence of severe sporadic cases of HFRS.