[Herd immunity to SARS-CoV-2 in the Novosibirsk Region population amid the COVID-19 pandemic].

AIM: To determine the level of SARS-CoV-2 seroprevalence among the Novosibirsk Region population against the background of the COVID-19 pandemic. MATERIAL AND METHODS: The work was carried out in 2 phases: 1) a cross-sectional cohort study performed 28.06- 15.07.2020; 2) longitudinal cohort 3-stage seromonitoring: 1st stage 28.06-15.07.2020; 2nd 14.09-04.10.2020; 3rd 10-30.12.2020 The work was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of St-Petersburg Pasteur Institute, taking into account the recommendations of the WHO. IgG antibodies to the SARS-CoV-2 nucleocapsid protein were detected by ELISA using a kit of reagents produced by the SRCMSB (Obolensk) according to the manufacturer's instructions. Statistical analysis was performed using Microsoft Excel 2010 and other programs. RESULTS: The seroprevalence in the region's population was 9.1% (95% CI 8.0-10.2): maximum in children 14-17 years old (17.6%, 95% CI 12.3-23.9) and persons over 75 years (14.8%, 95% CI 11.4-18.8), minimum among persons 30-39 years old (4.9%, 95% CI 3.0-8.0). Increased rate was noted among the unemployed (15.4%, 95% CI 9.9-17.1) and other individuals (13.0%, 95% CI 8.6-18.5). Seroprevalence was 33.3% (95% CI 16.3-59.0) in COVID-19 convalescents and 19.0% (95% CI 13.9-25.0) in contact persons. More than 94.7% (95% CI 91.2-97.2) of seropositive individuals were asymptomatic. During the serological monitoring, seroprevalence increased from 7.4% (95% CI 6.2-8.9) at 1st stage 1 to 12.4% (95% CI 10.6-14.3) at 2nd , and 31% (95% CI 28.8-33.3) at 3rd stage. CONCLUSION: SARS-CoV-2 herd immunity has not reached the threshold level, this does not exclude exacerbation of the epidemic process.

[Detection of arbovirus antigens in the mosquitoes and ticks inhabiting the Saratov Region].

The paper gives the results of a study dealing with the detection of the antigens of arboviruses of West Nile, Sindbis, Batai, Crimean-Congo hemorrhagic fever, a serocomplex of Californian encephalitis in the field material gathered in the Saratov Region in 2000-2006. The bloodsucking arthropods inhabiting the region were shown to be actively involved in the circulation of arboviruses in natural biotopes. The conclusion that it is expedient to organize an annual monitoring of arbovirus-induced infections in the areas where positive findings have been notified is justified.

[The ecology and prevalence of arboviruses on the territory of the Saratov Region].

The territorial spread of Tahyna, Batai, Sindbis, West Nile fever and Crimean-Congo hemorrhagic fever viruses throughout the Saratov region in 1998 - 2000 was analyzed. The characteristics of the epizootic activity of the natural foci of these arboviruses in different landscape zones (temperate forest-steppes, steppes and semi-deserts) were calculated. The species composition of small mammals, the natural reservoirs of the causative agents of arbovirus infections, was determined.

On the off-Bragg reflectivity enhancement in dynamical multiple diffraction of X-rays by an In(0.5)Ga(0.5)P/GaAs heteroepitaxial structure.

The effect of dynamical interactions between reflections involved in 000/111/220 multiple diffraction by an In(0.5)Ga(0.5)P/GaAs heteroepitaxial structure was observed, which significantly increases the intensity of the (111) reflection in the region of the total (220) reflection from the substrate during Renninger-like scanning. The amplitude of the peak is roughly five times as great as the peak of detoured excitation for ideal GaAs. Possible applications of the observed feature in synchrotron-radiation-based studies are discussed.

Virulence of pPst+ and pPst- strains of Yersinia pestis for guinea-pigs.

Guinea-pigs were infected subcutaneously or by respiratory challenge with plasmid-containing (pPst+pCad+pFra+) Yersinia pestis strain 358 and its pPst-pCad+pFra+, pPst+pCad+pFra- and pPst-pCad+pFra- derivatives, grown in vitro at 28 degrees C or at 37 degrees C. Lack of plasmid pPst did not lead to an increase in LD50 with either route of challenge. When the virulence of the four Y. pestis strains grown at the two temperatures was compared, the LD50 values of those grown at 37 degrees C were lower. Respiratory challenge with cultures grown at 37 degrees C mimics the man-to-man pneumonic plague cycle. The average LD50 values decreased c. two-fold and 10-fold for pPst+ and pPst- Y. pestis variants, respectively. The data suggest that historical epidemic outbreaks of pneumonic plague in the human population residing in the Caucasus region where there are natural plague foci in common voles may have been caused by pPst- Y. pestis strains.

[Combined (associated) vaccination against quarantinable infections]. / Kompleksnaia (assotsiirovannaia) vaktsinatsiia protiv karantinnykh infektsii.

The presence of several active foci of infection of different etiology is an indication for complex (combined) immunization against these diseases. The scheme of complex (combined) immunization against plague, cholera and yellow fever has been experimentally substantiated and successfully tested on volunteers.

[Experimental study of the pulmonary form of plague, tularemia and pseudotuberculosis]. / Eksperimental'noe izuchenie legochnykh form chumy, tuliaremii i psevdotuberkuleza

There was revealed a regular reduction of plague, tularemia and pseudotuberculosis bacteria count in the lungs of guinea pigs the first 12 hours after aerosol infection. Generalization of the infectious process and associated septicemia occurred in pulmonary plague and pulmonary tularemia on the 1st-2nd day, and in pulmonary pseudotuberculosis - on the 4th-5th day. Limits of accumulation of the causative agents in the organs and the blood at various stages of the infectious process were established.