Epidemic manifestations of coronavirus infection caused by «omicron» genovariant in the Volgograd region

Abstract

The article is devoted to an urgent problem the study of the epidemic manifestations of the new coronavirus infection COVID-19 during the fourth wave of the rise in the incidence, which began in January 2022 in the Volgograd region.
 Materials and methods: We used the official statistical data of the Office of Rospotrebnadzor for the Volgograd Region on the incidence of COVID-19 and the results of SARS-CoV-2 genomic RNA sequencing. The main research method is epidemiological analysis. We analyzed the period from the beginning of the next increase in the incidence, coinciding with the almost complete replacement of other variants of SARS-CoV-2 by omicron (since January 16, 2022), until the decrease and stabilization of the incidence rates on March 30, 2022. Comparison of the epidemiological process indicators was carried out with the period before the appearance of the omicron genovariant (as of December 30, 2021).
 Results and discussion: Since mid-January 2022, there has been a sharp rise in the incidence of COVID-19 in the region up to 2,222 cases per day by mid-February and a subsequent decrease in incidence rates by the end of March. It has been established that the next wave of coronavirus infection is associated both with an increase in interpersonal contacts on holidays and the subsequent introduction of the infection into work and educational teams, and with the change of the SARS-CoV-2 genovariant to omicron. During 2.5 months of the fourth wave, 76,717 people fell ill with coronavirus, which is 36.6 % of the total number of cases registered over the entire observation period. Moreover, the proportion of cases in the age category up to 18 years has significantly increased (by 13.1 %). During the analyzed period, the proportion of cases with a mild course increased by 18.3 % (up to 88.6 %), and the percentage of cases of moderate severity decreased by 10.1% (up to 10.5 %), a severe course decreased by 4.1% (to 0.7 %), asymptomatic also decreased by 4.06 % and accounted for 0.14 % of the total number of detected cases of COVID-19. The share of pneumonia in the total morbidity for 2.5 months decreased by 16.8 % (to 1.6 %). In most cases, the treatment took place on an outpatient basis. The percentage of patients requiring hospitalization decreased to 18.5 %. There is a downward trend in the mortality rate from 4.3 % before the rise in incidence to 3.2 % as of March 30, 2022.
 Conclusions: In the Volgograd region, from January 14, 2022, another rise in the incidence of COVID-19 was registered with the maximum indicators for the entire observation period in February. The omicron genovariant, which has become dominant, has a higher contagiousness and is actively spreading in childrens groups. The disease is characterized by a milder clinical course in the form of acute respiratory viral infections, bronchitis, and a decrease in the proportion of deaths.