Features of the covid-19 epidemic and characteristics of patients during the spread of the delta SARS-COV-2 in Russia

Aim: To study the manifestations of the COVID-19 epidemic and the clinical and epidemiological characteristics of adult patients with a new coronavirus infection during the dominance of the Delta SARS-COV-2 in the Russian Federation. Materials and Methods : Study included patients aged ≥18 years with a laboratory-confirmed diagnosis of COVID-19, detected in the period from 09/01/2021 to 11/30/2021 (n= 2 619 298) in 85 Russian regions. Results : There were 2 periods of rise and decline in the COVID-19 incidence and mortality during the spread of the Delta SARS-CoV-2 in Russia: June-September and OctoberDecember 2021 (Wald – Wolfowitz criterion, p<0,05). The median age of patients was 49 [36–63] years, 61,1% were women. Most of patients were 30–39 years old (21,0%), the lowest proportion was among 18–29 years old (12.1%) (p<0,05). Proportion of patients with mild disease was 75,4%, moderate – 18,8%, severe – 3,3%, extremely severe – 2,5% (p<0.05). Hospitalization rate was 23,7%, proportion of patients treated in the intensive care unit was 12.9%, and rate of invasive mechanical ventilation was 9,8%. The median period from the onset of symptoms to the diagnosis was 3 [1-6] days, the duration of the disease and hospitalization was 13,0 [10–16] and 12,0 [9–17] days, respectively. The median age of the deceased patients was 73 [65–82] years, of which 59,1% were women, 61,5% were persons ≥70 years old. The presence of one or more comorbidities was found in 73,9% of deceased patients (OR=17,1; 95% CI: 16,8–17,3). Conclusion : during the period of the spread of the Delta SARS-COV-2 variant in Russia, the number of patients with severe and extremely severe disease among adult patients without taking into account the vaccine history was 5,8%. Old age and the presence of concomitant diseases were key risk factors for adverse outcomes of COVID-19.