NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 48 of 2025 (24.11.25 - 30.11.25)

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 (78.6 per 10 000 of population) was lower than national baseline (82.9) by 5.2%.

Etiology of ILI & ARI. Among 11104 patients investigation 1229 (11.1%) respiratory samples were positive for influenza, including 220 cases of unsubtyped influenza A in 10 cities, 85 cases of influenza A(H1N1)pdm09 in 9 cities, 914 cases of influenza A(H3N2) in 41 cities and 10 cases of influenza B in 5 cities.

21 influenza viruses A(H3N2) were isolated on MDCK cell culture in Moscow (2) in Novosibirsk (8), Samara (3), Saint-Petersburg (5) and Ulan-Ude (3). Since the beginning of the season 39 influenza viruses A(H3N2) were isolated.

Antigenic characterization. Since the beginning of the season 2025-2026 11 influenza have been antigenically characterized by the NICs in Saint-Petersburg and Moscow, including: 1 influenza A(H1N1)pdm09 virus and 10 influenza A(H3N2) viruses. Virus A(H1N1)pdm09 was similar to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2025-2026 season. 9 influenza A(H3N2) viruses were a drift variant of the reference strain A/Croatia/10136RV/23, also recommended in vaccines for countries in the Northern Hemisphere for the 2025-2026 season, 1 virus A(H3N2) was similar to the reference strain A/Thailand/8/2022.

Genetic characterization. Since the beginning of the season 2025-2026 sequenced 7 influenza viruses in Saint-Petersburg. 5 influenza A(H3N2) viruses were similar to the vaccine strain A/Croatia/10136RV/2023, of which 3 viruses belong to clade 3C.2a1b.2a.2a.3a.1 subclade K, 2 viruses belong to clade 3C.2a1b.2a.2a.3a.1. 2 A(H1N1)pdm09 viruses were similar to the vaccine strain A/Victoria/4897/2022 and were classified as clade 6B.1A.5a.2a.1.

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 13.6% (PCR).

In sentinel surveillance system clinical samples from 15 SARI patients were investigated by rRT-PCR for influenza, among them 2 (13.3%) cases of influenza A(H3N2) were recognized. Among 15 SARI sample no positive case of coronavirus SARS-CoV-2 was recognized. Among 15 SARI samples 1 (6.7%) case of PIV infection were detected. 

Among from 12 ILI/ARI patients no positive cases of influenza were recognized. Among 12 ILI/ARI samples no positive cases of ARVI were recognized. Among 12 ILI/ARI samples no positive cases of coronavirus SARS-CoV-2 were recognized.COVID-19. According to the data obtained by NIC in Saint-Petersburg totally 14061 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 was detected in 369 (2.6%) cases.

Influenza and ARI morbidity data

Epidemiological data showed increased of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (78.6 per 10 000 of population) was lower than national baseline (82.9) by 5.2%.

Incidence rate of clinically diagnosed influenza increased comparing to previous week and amounted to 1.44 per 10 000 of population, it was higher than pre-epidemic MEM baseline (0.45).

Hospitalization rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.32 per 10 000 of population, it was higher than pre-epidemic MEM baseline (0.099).

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 11104 patients investigation 1229 (11.1%) respiratory samples were positive for influenza, including 220 cases of unsubtyped influenza A in 10 cities, 85 cases of influenza A(H1N1)pdm09 in 9 cities, 914 cases of influenza A(H3N2) in 41 cities and 10 cases of influenza B in 5 cities.

21 influenza viruses A(H3N2) were isolated on MDCK cell culture in Moscow (2) in Novosibirsk (8), Samara (3), Saint-Petersburg (5) and Ulan-Ude (3). Since the beginning of the season 39 influenza viruses A(H3N2) were isolated.

Antigenic characterization. Since the beginning of the season 2025-2026 11 influenza have been antigenically characterized by the NICs in Saint-Petersburg and Moscow, including: 1 influenza A(H1N1)pdm09 virus and 10 influenza A(H3N2) viruses. Virus A(H1N1)pdm09 was similar to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2025-2026 season. 9 influenza A(H3N2) viruses were a drift variant of the reference strain A/Croatia/10136RV/23, also recommended in vaccines for countries in the Northern Hemisphere for the 2025-2026 season, 1 virus A(H3N2) was similar to the reference strain A/Thailand/8/2022.Genetic characterization. Since the beginning of the season 2025-2026 sequenced 7 influenza viruses in Saint-Petersburg. 5 influenza A(H3N2) viruses were similar to the vaccine strain A/Croatia/10136RV/2023, of which 3 viruses belong to clade 3C.2a1b.2a.2a.3a.1 subclade K, 2 viruses belong to clade 3C.2a1b.2a.2a.3a.1. 2 A(H1N1)pdm09 viruses were similar to the vaccine strain A/Victoria/4897/2022 and were classified as clade 6B.1A.5a.2a.1.

ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) was estimated 13.6% of investigated samples by PCR.

Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 48 of 2025

COVID-19. According to the data obtained by NIC in Saint-Petersburg totally 14061 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 was detected in 369 (2.6%) cases.

Table 2. Results of influenza viruses isolation in Russia, week 48 of 2025

Sentinel influenza surveillance

Clinical samples from 15 SARI patients were investigated by rRT-PCR for influenza, among them 2 (13.3%) cases of influenza A(H3N2) were recognized. Among 15 SARI sample no positive case of coronavirus SARS-CoV-2 was recognized. Among 15 SARI samples 1 (6.7%) case of PIV infection were detected.

Among 12 ILI/ARI patients no positive cases of influenza were recognized. Among 12 ILI/ARI samples no positive cases of ARVI were recognized. Among 12 ILI/ARI samples no positive cases of coronavirus SARS-CoV-2 were recognized.