Influenza Bulletin
NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION
week 5 of 2025 (27.01.25 - 02.02.25)
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 (68.7 per 10 000 of population) was lower than national baseline (89.9) by 23.6%.
Etiology of ILI & ARI. Among 12039 patients investigation 1532 (12.7%) respiratory samples were positive for influenza, including 245 cases of unsubtyped influenza A in 10 cities, 777 cases of influenza A(H1N1)pdm09 in 41 cities, 24 cases of influenza A(H3N2) in 7 cities and 486 cases of influenza B in 37 cities.
40 influenza viruses were isolated on MDCK cell culture, including 30 cases of influenza A(H1N1)pdm09 in Astrakhan (2), Vladimir (4), Yekaterinburg (1), Kaliningrad (1), Moscow (2), Novosibirsk (4), Orenburg (2), Samara (2), Saint-Petersburg (6), Stavropol (4), Ulan-Ude (2) and 10 cases of influenza B in Astrakhan (1), Moscow (1), Samara (2), Saint-Petersburg (1), Stavropol (4), and Yaroslavl (1). Since the beginning of the season 92 influenza viruses, including: 71 A(H1N1)pdm09 viruses, 3 - A(H3N2) and 18 influenza B viruses.
Antigenic characterization. Since the beginning of the season 40 influenza have been antigenically characterized by the NICs, including: 30 influenza A(H1N1)pdm09, 2 influenza A(H3N2) and 8 influenza B viruses. 29 A(H1N1)pdm09 viruses were similar to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2024-2025 season, one A(H1N1)pdm09 strain reacted to a 1:8 homologous titer with serum to the vaccine strain. One A(H3N2) strain was similar to the vaccine strain A/Thailand/8/22, the other interacted to 1:8 homologous titer with serum to the A/Thailand/8/22 vaccine strain. All 8 influenza B viruses were similar to vaccine strain B/Austria/1359417/2021.
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 2024-2025, the sensitivity of 40 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in NIC Saint-Petersburg, including: 31 A(H1N1)pdm09 influenza viruses, 2 A(H3N2) influenza viruses and 7 influenza B viruses. All studied viruses were sensitive to neuraminidase inhibitors.
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 14.5% (PCR).
In sentinel surveillance system clinical samples from 23 SARI patients were investigated by rRT-PCR for influenza, among them 3 (13.0%) case of influenza A(H1N1)pdm09 were recognized. Among 23 SARI patients no positive cases of coronavirus SARS-CoV-2 recognized. Among 23 SARI samples 1 (4.3%) case positive of RhV infection were detected.
Clinical samples from 42 ILI/ARI patients were investigated by rRT-PCR for influenza, among them 3 (7.1%) cases of influenza were recognized, including 2 cases of A(H1N1)pdm09 and 1 case of influenza B. Among 21 ILI/ARI samples 1 (4.8%) case positive of CoV infection was detected. Among 42 ILI/ARI patients no positive cases of coronavirus SARS-CoV-2 recognized.
COVID-19. Totally 24 893 662 cases and 404 355 deaths associated with COVID-19 were registered in Russia including 7985 cases and 20 deaths in week 05. According to the data obtained by NIC in Saint-Petersburg totally 12977 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 284 (2.2%) cases.
Influenza and ARI morbidity data

Weeks
-
Morbidity 2024/25
-
Morbidity 2023/24
-
MEM baseline 2024/25
Epidemiological data showed increase of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (68.7 per 10 000 of population) was lower than national baseline (89.9) by 23.6%.

Weeks
-
Season 2024/25
-
Season 2023/24
-
MEM baseline
Incidence rate of clinically diagnosed influenza increased comparing to previous week and amounted to 1.38 per 10 000 of population, it was higher than pre-epidemic MEM baseline (0.040).

Weeks
-
Season 2024/25
-
Season 2023/24
-
MEM baseline
Hospitalization rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.31 per 10 000 of population, it was higher 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 48 RBLs and two WHO NICs. According to these data as a result of 12039 patients investigation 1532 (12.7%) respiratory samples were positive for influenza, including 245 cases of unsubtyped influenza A in 10 cities, 777 cases of influenza A(H1N1)pdm09 in 41 cities, 24 cases of influenza A(H3N2) in 7 cities and 486 cases of influenza B in 37 cities.
40 influenza viruses were isolated on MDCK cell culture, including 30 cases of influenza A(H1N1)pdm09 in Astrakhan (2), Vladimir (4), Yekaterinburg (1), Kaliningrad (1), Moscow (2), Novosibirsk (4), Orenburg (2), Samara (2), Saint-Petersburg (6), Stavropol (4), Ulan-Ude (2) and 10 cases of influenza B in Astrakhan (1), Moscow (1), Samara (2), Saint-Petersburg (1), Stavropol (4), and Yaroslavl (1). Since the beginning of the season 92 influenza viruses, including: 71 A(H1N1)pdm09 viruses, 3 - A(H3N2) and 18 influenza B viruses.
Antigenic characterization. Since the beginning of the season 40 influenza have been antigenically characterized by the NICs, including: 30 influenza A(H1N1)pdm09, 2 influenza A(H3N2) and 8 influenza B viruses. 29 A(H1N1)pdm09 viruses were similar to the reference strain A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2024-2025 season, one A(H1N1)pdm09 strain reacted to a 1:8 homologous titer with serum to the vaccine strain. One A(H3N2) strain was similar to the vaccine strain A/Thailand/8/22, the other interacted to 1:8 homologous titer with serum to the A/Thailand/8/22 vaccine strain. All 8 influenza B viruses were similar to vaccine strain B/Austria/1359417/2021.
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 2024-2025, the sensitivity of 40 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in NIC Saint-Petersburg, including: 31 A(H1N1)pdm09 influenza viruses, 2 A(H3N2) influenza viruses and 7 influenza B viruses. All studied viruses were sensitive to neuraminidase inhibitors.

-
No data
-
No viruses detected
-
H1pdm09
-
H3
-
H3+H1pdm09
-
B
-
B+H1pdm09
-
B+H3
-
B+H3+H1pdm09
-
A (not subt.)
-
A (not subt.)+H1pdm09
-
A (not subt.)+H3
-
A (not subt.)+H3+H1pdm09
-
A (not subt.)+B
-
A (not subt.)+B+H1pdm09
-
A (not subt.)+B+H3
-
A (not subt.)+B+H3+H1pdm09

Weeks
-
H1pdm09
-
H3
-
B
-
A (not subt.)
-
% positive

Weeks
-
PIV
-
ADV
-
RSV
-
RhV
-
CoV
-
MPV
-
BoV
ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) estimated as 14.5% of investigated samples by PCR.

Weeks
-
H1pdm09
-
H3
-
B
-
% positive
Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 5 of 2025
Number of specimens / number of positive cases | % positive | |
Influenza | ||
Number of specimens tested for influenza | 12039 | - |
Influenza A (not subt.) | 245 | 2,0% |
Influenza A(H1)pdm09 | 777 | 6,5% |
Influenza A(H3) | 24 | 0,2% |
Influenza B | 486 | 4,0% |
All influenza | 1532 | 12,7% |
Other ARVI | ||
Number of specimens tested for ARVI | 11931 | - |
PIV | 75 | 0,6% |
ADV | 153 | 1,3% |
RSV | 240 | 2,0% |
RhV | 587 | 4,9% |
CoV | 529 | 4,4% |
MPV | 38 | 0,3% |
BoV | 110 | 0,9% |
All ARVI | 1732 | 14,5% |
SARS-CoV-2 (COVID-19) | ||
Number of specimens tested for SARS-CoV-2 | 12977 | - |
SARS-CoV-2 | 284 | 2,2% |

-
No data
-
less then 10%
-
10-20%
-
20-30%
-
30-40%
-
40-50%
-
50% and more
COVID-19. Totally 24 893 662 cases and 404 355 deaths associated with COVID-19 were registered in Russia including 7985 cases and 20 deaths in week 05. According to the data obtained by NIC in Saint-Petersburg totally 12977 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 284 (2.2%) cases.
Table 2. Results of influenza viruses isolation in Russia, week 5 of 2025
Number of specimens / number of viruses | % isolated viruses | |
Number of specimens | 95 | - |
Influenza A(H1)pdm09 | 30 | 31,6% |
Influenza A(H3) | 0 | 0,0% |
Influenza B | 10 | 10,5% |
All influenza | 40 | 42,1% |
Sentinel influenza surveillance
Clinical samples from 23 SARI patients were investigated by rRT-PCR for influenza, among them 3 (13.0%) case of influenza A(H1N1)pdm09 were recognized. Among 23 SARI patients no positive cases of coronavirus SARS-CoV-2 recognized. Among 23 SARI samples 1 (4.3%) case positive of RhV infection was detected.
Clinical samples from 42 ILI/ARI patients were investigated by rRT-PCR for influenza, among them 3 (7.1%) cases of influenza were recognized, including 2 cases of A(H1N1)pdm09 and 1 case of influenza B. Among 21 ILI/ARI samples 1 (4.8%) case positive of CoV infection was detected. Among 42 ILI/ARI patients no positive cases of coronavirus SARS-CoV-2 recognized.

Weeks
-
H1pdm09
-
H3
-
B
-
A (not subt.)
-
% positive

Weeks
-
H1pdm09
-
H3
-
B
-
A (not subt.)
-
% positive

Weeks
-
PIV
-
ADV
-
RSV
-
RhV
-
CoV
-
MPV
-
BoV

Weeks
-
PIV
-
ADV
-
RSV
-
RhV
-
CoV
-
MPV
-
BoV