National Weekly Bulletin

NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 46 of 2024 (11.11.24 - 17.11.24)

Summary

Influenza and ARI incidence data. Influenza and other ARI activity in Russia increased in comparison with previous week. The nationwide ILI and ARI morbidity level (61.2 per 10 000 of population) was lower than national baseline (70.0) by 12.6%.

Etiology of ILI & ARI. Among 10018 patients investigation 19 (0.2%) respiratory samples were positive for influenza, including 2 cases of unsubtyped influenza A in 2 cities, 4 cases of influenza A(H1N1)pdm09 in 3 cities and 13 cases of influenza B in 5 cities.

One influenza virus B was isolated on MDCK cell culture in Saint-Petersburg. Since the beginning of the season 3 influenza viruses were isolated on MDCK cell culture in Saint-Petersburg, including: 1 A(H1N1)pdm09 virus, 1 A(H3N2) virus and 1 B virus.

Antigenic characterization. The first influenza A(H1N1)pdm09 virus isolated in Saint-Petersburg (NIC) from a patient from the city of Volzhsk in the 2024-2025 epidemic season was antigenically characterized. The virus reacted to 1:8 homologous titer with serum to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2024-2025 season.  

Genetic analysis. Since the beginning of the season 2023-2024, sequencing of 6 A(H1N1)pdm09 influenza isolates, 1779 influenza viruses and isolates from primary clinical materials from patients and 50 B influenza isolates were performed. According to phylogenetic analysis, 6 A(H1N1)pdm09 influenza isolates were assigned to genetic clade 6B.1A.5a.2a and similar to the vaccine strain A/Victoria/2570/2019, 1762 influenza A(H3N2) viruses were assigned to genetic clade 3C.2a1b.2a.2а.3а.1 and similar to the reference strain A/Thailand/08/2022, 16 viruses were assigned to genetic clade 2a.3b and similar to the reference virus A/Sydney/732/2022 and 1 strain - assigned to clade 3C.2a.1b.2a.2a.2a.3b and similar to the reference virus A/Sydney/732/2022. 50 B influenza isolates were assigned to genetic subclade V1A.3a.2 and similar to the vaccine strain B/Austria/1359417/2021. All viruses were sensitive to neuraminidase inhibitors (oseltamivir, zanamivir).

Susceptibility to antivirals. Since the beginning of the season 2023-2024, the sensitivity of 616 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in two NICs (Moscow, Saint-Petersburg), including 4 A(H1N1)pdm09 influenza viruses, 604 A(H3N2) influenza viruses and 8 influenza B virus. All studied viruses were sensitive to neuraminidase inhibitors, except for 2 strain of A(H3N2) isolated in Moscow, which showed reduced sensitivity to oseltamivir.

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 13.7% (PCR).

In sentinel surveillance system clinical samples from 38 SARI patients were investigated by rRT-PCR for influenza, among them no positive cases recognized. Among 38 SARI patients no positive cases of coronavirus SARS-CoV-2 recognized. Among 38 SARI samples 8 (21.1%) cases positive for ARVI were detected including: 5 cases of PIV, 1 case of ADV, 1 case of RhV and 1 case of BoV infection.

Clinical samples from 40 ILI/ARI patients were investigated by rRT-PCR for influenza, among them no positive cases recognized. Among 21 ILI/ARI samples 4 (19.0%) cases positive for ARVI were detected including: 1 case of PIV, 2 cases of RhV and 1 case of BoV infection. 1 (2.7%) of 37 ILI/ARI patients were positive for coronavirus SARS-CoV-2.

COVID-19. Totally 24 670 411 cases and 403 885 deaths associated with COVID-19 were registered in Russia including 25 108 cases and 46 deaths in week 46. According to the data obtained by NIC in Saint-Petersburg totally 18986 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 791 (4.2%) cases.

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 (61.2 per 10 000 of population) was lower than national baseline (70.0) by 12.6%.

Incidence rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.027 per 10 000 of population, it was lower than pre-epidemic MEM baseline (0.040).

Hospitalization rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.0033 per 10 000 of population, it was lower than pre-epidemic MEM baseline (0.010).

Influenza and ARVI laboratory testing results

Cumulative results of influenza laboratory diagnosis by rRT-PCR were submitted by 44 RBLs and two WHO NICs. According to these data as a result of 10018 patients investigation 19 (0.2%) respiratory samples were positive for influenza, including 2 cases of unsubtyped influenza A in 2 cities, 4 cases of influenza A(H1N1)pdm09 in 3 cities and 13 cases of influenza B in 5 cities.

One influenza virus B was isolated on MDCK cell culture in Saint-Petersburg. Since the beginning of the season 3 influenza viruses were isolated on MDCK cell culture in Saint-Petersburg, including: 1 virus A(H1N1)pdm09, 1 virus A(H3N2) and 1 virus B.

Antigenic characterization. The first influenza A(H1N1)pdm09 virus isolated in Saint-Petersburg (NIC) of the a patient from the city of Volzhsk in the 2024-2025 epidemic season was antigenically characterized. The virus reacted to 1:8 homologous titer with serum to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2024-2025 season.

Genetic analysis. Since the beginning of the season 2023-2024, sequencing of 6 A(H1N1)pdm09 influenza isolates, 1779 influenza viruses and isolates from primary clinical materials from patients and 50 B influenza isolates were performed. According to phylogenetic analysis, 6 A(H1N1)pdm09 influenza isolates were assigned to genetic clade 6B.1A.5a.2a and similar to the vaccine strain A/Victoria/2570/2019, 1762 influenza A(H3N2) viruses were assigned to genetic clade 3C.2a1b.2a.2а.3а.1 and similar to the reference strain A/Thailand/08/2022, 16 viruses were assigned to genetic clade 2a.3b and similar to the reference virus A/Sydney/732/2022 and 1 strain - assigned to clade 3C.2a.1b.2a.2a.2a.3b and similar to the reference virus A/Sydney/732/2022. 50 B influenza isolates were assigned to genetic subclade V1A.3a.2 and similar to the vaccine strain B/Austria/1359417/2021. All viruses were sensitive to neuraminidase inhibitors (oseltamivir, zanamivir).

Susceptibility to antivirals. Since the beginning of the season 2023-2024, the sensitivity of 616 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in two NICs (Moscow, Saint-Petersburg), including 4 A(H1N1)pdm09 influenza viruses, 604 A(H3N2) influenza viruses and 8 influenza B virus. All studied viruses were sensitive to neuraminidase inhibitors, except for 2 strain of A(H3N2) isolated in Moscow, which showed reduced sensitivity to oseltamivir.

ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) estimated as 13.7% of investigated samples by PCR.

Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 46 of 2024

COVID-19. Totally 24 670 411 cases and 403 885 deaths associated with COVID-19 were registered in Russia including 25 108 cases and 46 deaths in week 46. According to the data obtained by NIC in Saint-Petersburg totally 18986 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 791 (4.2%) cases.

Table 2. Results of influenza viruses isolation in Russia, week 46 of 2024

Sentinel influenza surveillance

Clinical samples from 38 SARI patients were investigated by rRT-PCR for influenza, among them no positive cases recognized. Among 38 SARI patients no positive cases of coronavirus SARS-CoV-2 recognized. Among 38 SARI samples 8 (21.1%) cases positive for ARVI were detected including: 5 cases of PIV, 1 case of ADV, 1 case of RhV and 1 case of BoV infection.

Clinical samples from 40 ILI/ARI patients were investigated by rRT-PCR for influenza, among them no positive cases recognized. Among 21 ILI/ARI samples 4 (19.0%) cases positive for ARVI were detected including: 1 case of PIV, 2 cases of RhV and 1 case of BoV infection. 1 (2.7%) of 37 ILI/ARI patients were positive for coronavirus SARS-CoV-2.