NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION
week 20 of 2022 (16.05.22 - 22.05.22)
Influenza and ARI morbidity data
Epidemiological data increased of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (38.5 per 10 000 of population) was lower than national baseline (70.0) by 45.0%.
Incidence rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.0040 per 10 000 of population, it was much lower than pre-epidemic MEM baseline (0.060).
Hospitalization rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.0024 per 10 000 of population, it was much lower than pre-epidemic MEM baseline (0.040).
Influenza and ARVI laboratory testing results
Cumulative results of influenza laboratory diagnosis by rRT-PCR were submitted by 42 RBLs and two WHO NICs. According to these data as a result of 2754 patients investigation 16 (0.6%) respiratory samples positive for influenza B were detected in 4 cities.
Antigenic characterization. Since the beginning of the season, 347 influenza A(H3N2) and 25 influenza B viruses have been antigenically characterized by the NICs (Moscow and Saint-Petersburg). 60 A(H3N2) viruses were antigenically closely related to vaccine strain A/Cambodia/e0826360/20 (H3N2), included in vaccines recommended by the WHO for the Northern Hemisphere for the 2021-2022 season, 12 strains were poorly recognized (1/16-1/32 of the homological titer) by rat antiserum to vaccine strain. 274 viruses were antigenically similar to reference strain A/Darwin/9/2021 (H3N2), one strain reacted with rat antiserum to reference strain in an 1/16 of the homological titer. One influenza B virus was antigenically similar to reference strain B/Washington/02/19, one influenza B virus (Victorian line) reacted with rat antiserum to vaccine strain B/Washington/02/19 in an 1/16 of the homological titer and 23 influenza B viruses were antigenically closely related to Victoria line reference strain B/Austria/1359417/2021.
Genetic characterization. Since the beginning of the season 31 influenza viruses and 201 PCR positive samples have been genetically characterized by the NIC (Saint-Petersburg). Phylogenetic analysis of 228 A(H3N2) viruses showed that they all belonged to genetic group 3C.2a1b.2a.2. And 4 influenza B viruses belonged to genetic group V1A.3a.2.
Susceptibility to antivirals. All 267 influenza A(H3N2) viruses and 10 influenza B viruses analysed by the two NIC (Moscow, Saint-Petersburg) were susceptible to oseltamivir and zanamivir.
ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) estimated as 13.3% of investigated samples by PCR.
Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 20 of 2022
|Number of specimens / number of positive cases||% positive|
|Number of specimens tested for influenza||2754||-|
|Influenza A (not subt.)||0||0,0%|
|Number of specimens tested for ARVI||2666||-|
|Number of specimens tested for SARS-CoV-2||8410||-|
COVID-19. Totally 18 310 673 cases and 378 700 deaths associated with COVID-19 were registered in Russia including 4 700 cases and 91 deaths in last 24 hours (on 12:00 of 26.05.2022). According to the data obtained by NIC in Saint-Petersburg totally 8 410 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 950 (11.3%) cases.
Table 2. Results of influenza viruses isolation in Russia, week 20 of 2022
|Number of specimens / number of viruses||% isolated viruses|
|Number of specimens||5||-|
Sentinel influenza surveillance
Clinical samples from 35 SARI patients were investigated by rRT-PCR for influenza, among them no positive cases recognized. 28 SARI patients were investigated for ARVI by rRT-PCR, among them 5 (17.9%) cases of ARVI recognized including 2 cases of ADV, 1 case of RSV, 1 case of CoV and 1 case of MPV. Among 35 ILI/ARI patients no positive cases of coronavirus SARS-CoV-2 recognized.
Clinical samples from 41 ILI/ARI patients were investigated for influenza by rRT-PCR, among them no positive cases recognized. Among 29 ILI/ARI samples 7 (24.1%) cases positive for ARVI detected including 2 cases of PIV, 3 cases of RhV, 1 case of CoV and 1 case of BoV infection. Among 39 ILI/ARI patients no positive cases of coronavirus SARS-CoV-2 recognized.