National Weekly Bulletin

NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 5 of 2023 (30.01.23 - 05.02.23)

Summary

Influenza and ARI incidence data. Influenza and other ARI activity increase of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (86.6 per 10 000 of population) was higer than national baseline (70.0) by 23.7%.

Etiology of ILI & ARI. Among 9145 patients investigation 1191 (13.0%) respiratory samples were positive for influenza, including 218 cases of influenza A(H1N1)pdm09 in 31 cities, 2 cases of influenza A(H3N2) in 1 city, 106 cases of influenza A unsubtyped in 10 cities and 865 cases of influenza B in 38 cities.

91 influenza viruses were isolated on MDCK cell culture, including: 45 influenza A(H1N1)pdm09 viruses in Vladivostok (5), Yekaterinburg (2), Kaliningrad (2), Moscow (3), Novosibirsk (1), Orenburg (3), Saint-Petersburg (14), Stavropol (6), Tomsk (9); 46 influenza B viruses in in Astrakhan (2), Vladivostok (6), Yekaterinburg (5), Kaliningrad (2), Krasnoyarsk (2), Novosibirsk (2), Samara (2), Saint-Petersburg (14), Stavropol (1), Tomsk (1), Khabarovsk (9). Since the beginning of the season 755 influenza viruses were isolated on MDCK cell culture, including: 609 viruses A(H1N1)pdm09, 19 viruses A(H3N2) and 127 viruses B.

Antigenic characterization. Since the beginning of the season, 252 influenza A(H1N1)pdm09 viruses have been antigenically characterized by the NICs, including: Moscow (38) and Saint-Petersburg (214), 10 influenza A(H3N2) viruses in Saint-Petersburg and 40 influenza B, including: Moscow (5) and Saint-Petersburg (35). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. All A(H3N2) strains were similar to the reference virus A/Darwin/9/2021. 39 influenza B viruses were antigenically similar to reference strain ÷/Austria/1359417/2021 and 1 influenza B virus reacted with the reference virus antiserum to a 1:8 homologous titer.

Genetic analysis. Sequencing of 218 influenza viruses from primary clinical materials from patients was performed by the NIC (Saint-Petersburg). According to phylogenetic analysis, 208 influenza A(H1N1)pdm09 viruses were assigned to genetic subgroup 6 B.1A.5a.2 and similar to reference virus A/Victoria/2570/2019 (H1N1)pdm09; 1 A(H3N2) virus was assigned to subgroup 3C.2 a1b.2a.2 and similar to reference virus Bangladesh/4005/2020 (H3N2); 9 influenza type B viruses were assigned to genetic subgroup V1A.3a.2 reference virus B/Austria/1359417/2021.Susceptibility to antivirals. All 58 influenza A(H1N1)pdm09 viruses analysed by the NIC (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) was estimated in total as 12.5% (PCR).

In sentinel surveillance system clinical samples from 75 SARI patients were investigated by rRT-PCR for influenza, among them 11 (14.7%) cases of influenza, including 1 case of influenza A(H1N1)pdm09, 9 cases of influenza B and 1 case of influenza A unsubtyped. Among 46 SARI samples 12 (26.1%) cases positive for ARVI detected including 2 cases of ADV, 2 cases of RSV, 5 cases of RhV, 2 cases of MPV and 1 case of BoV infection. 5 (9.6%) of 52 SARI patients were positive for coronavirus SARS-CoV-2. 

Clinical samples from 70 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 5 (7.1%) cases of influenza B. Among 57 ILI/ARI samples 14 (24.6%) cases positive for ARVI detected including 1 case of PIV, 2 cases of ADV, 6 cases of RhV, 3 cases of CoV and 2 cases of MPV infection. 7 (11.3%) of 62 ILI/ARI patients were positive for coronavirus SARS-CoV-2.  

COVID-19. Totally 22 035 133 cases and 395 447 deaths associated with COVID-19 were registered in Russia including 12 301 cases and 41 deaths in last 24 hours (on 12:00 of 09.02.2023). According to the data obtained by NIC in Saint-Petersburg totally 10 517 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 901 (8.6%) cases.

Influenza and ARI morbidity data

Epidemiological data showed increase of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (86.6 per 10 000 of population) was higer than national baseline (70.0) by 23.7%.

Incidence rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.80 per 10 000 of population, it was higer than pre-epidemic MEM baseline (0.060).

Hospitalization rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.21 per 10 000 of population, it was higer 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 46 RBLs and two WHO NICs. According to these data as a result of 9145 patients investigation 1191 (13.0%) respiratory samples were positive for influenza, including 218 cases of influenza A(H1N1)pdm09 in 31 cities, 2 cases of influenza A(H3N2) in 1 city, 106 cases of influenza A unsubtyped in 10 cities and 865 cases of influenza B in 38 cities.

91 influenza viruses were isolated on MDCK cell culture, including: 45 influenza A(H1N1)pdm09 viruses in Vladivostok (5), Yekaterinburg (2), Kaliningrad (2), Moscow (3), Novosibirsk (1), Orenburg (3), Saint-Petersburg (14), Stavropol (6), Tomsk (9); 46 influenza B viruses in in Astrakhan (2), Vladivostok (6), Yekaterinburg (5), Kaliningrad (2), Krasnoyarsk (2), Novosibirsk (2), Samara (2), Saint-Petersburg (14), Stavropol (1), Tomsk (1), Khabarovsk (9). Since the beginning of the season 755 influenza viruses were isolated on MDCK cell culture, including: 609 viruses A(H1N1)pdm09, 19 viruses A(H3N2) and 127 viruses B.

Antigenic characterization. Since the beginning of the season, 252 influenza A(H1N1)pdm09 viruses have been antigenically characterized by the NICs, including: Moscow (38) and Saint-Petersburg (214), 10 influenza A(H3N2) viruses in Saint-Petersburg and 40 influenza B, including: Moscow (5) and Saint-Petersburg (35). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. All A(H3N2) strains were similar to the reference virus A/Darwin/9/2021. 39 influenza B viruses were antigenically similar to reference strain ÷/Austria/1359417/2021 and 1 influenza B virus reacted with the reference virus antiserum to a 1:8 homologous titer.Genetic analysis. Sequencing of 218 influenza viruses from primary clinical materials from patients was performed by the NIC (Saint-Petersburg). According to phylogenetic analysis, 208 influenza A(H1N1)pdm09 viruses were assigned to genetic subgroup 6 B.1A.5a.2 and similar to reference virus A/Victoria/2570/2019 (H1N1)pdm09; 1 A(H3N2) virus was assigned to subgroup 3C.2 a1b.2a.2 and similar to reference virus Bangladesh/4005/2020 (H3N2); 9 influenza type B viruses were assigned to genetic subgroup V1A.3a.2 reference virus B/Austria/1359417/2021.Susceptibility to antivirals. All 58 influenza A(H1N1)pdm09 viruses analysed by the NIC (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 12.5% of investigated samples by PCR.

Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 5 of 2023

COVID-19. Totally 22 035 133 cases and 395 447 deaths associated with COVID-19 were registered in Russia including 12 301 cases and 41 deaths in last 24 hours (on 12:00 of 09.02.2023). According to the data obtained by NIC in Saint-Petersburg totally 10 517 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 901 (8.6%) cases.

Table 2. Results of influenza viruses isolation in Russia, week 5 of 2023

Sentinel influenza surveillance

ólinical samples from 75 SARI patients were investigated by rRT-PCR for influenza, among them 11 (14.7%) cases of influenza, including 1 case of influenza A(H1N1)pdm09, 9 cases of influenza B and 1 case of influenza A unsubtyped. Among 46 SARI samples 12 (26.1%) cases positive for ARVI detected including 2 cases of ADV, 2 cases of RSV, 5 cases of RhV, 2 cases of MPV and 1 case of BoV infection. 5 (9.6%) of 52 SARI patients were positive for coronavirus SARS-CoV-2. 

Clinical samples from 70 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 5 (7.1%) cases of influenza B. Among 57 ILI/ARI samples 14 (24.6%) cases positive for ARVI detected including 1 case of PIV, 2 cases of ADV, 6 cases of RhV, 3 cases of CoV and 2 cases of MPV infection. 7 (11.3%) of 62 ILI/ARI patients were positive for coronavirus SARS-CoV-2.