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Influenza Bulletin

Year: Week:

NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 42 of 2026 (12.10.26 - 18.10.26)

Summary

Influenza and ARI incidence data. Influenza and other ARI activity in Russia decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (56.9 per 10 000 of population) was lower than national baseline (82.9) by 31.4%.

Etiology of ILI & ARI. Among 7541 patients investigation 34 (0.5%) respiratory samples were positive for influenza, including 29 cases of influenza A(H1N1)pdm09 in 13 cities and 5 cases of influenza B in 1 city.

No influenza viruses were isolated on MDCK cell culture.

Antigenic characterization. Since the beginning of the season 2025-2026 649 influenza viruses have been antigenically characterized by the NICs in Saint-Petersburg and Moscow, including: 91 influenza A(H1N1)pdm09 viruses, 548 influenza A(H3N2) viruses and 10 influenza B viruses. 44 viruses A(H1N1)pdm09 were similar to the reference strains A/Victoria/4897/22 recommended in the vaccines for the Northern Hemisphere countries for the 2025-2026 season, 47 strains were a drift variant. 10 influenza A(H3N2) viruses were similar to the reference strain A/Croatia/10136RV/23, also recommended in vaccines for countries in the Northern Hemisphere for the 2025-2026 season, 526 A(H3N2) viruses were a drift variant, 11 viruses A(H3N2) were similar to the reference strain A/Thailand/8/2022, one strain was a drift variant of the reference strain A/Thailand/8/2022. 5 influenza B viruses were similar to the vaccine strain B/Austria/1359417/2021 and 5 strain were a drift variant of the reference strain B/Austria/1359417/2021.

Genetic characterization. Since the beginning of the season 2025-2026 sequenced 2677 influenza viruses in Saint-Petersburg. 2327 influenza A(H3N2) viruses were related to the vaccine strain A/Croatia/10136RV/2023 and belonged to the 3C.2a1b.2a.2a.3a.1 clade, of which 2192 viruses belonged to subclade K, 33 as subclade J.2.x, 98 as subclade J.2.2 and 4 as subclade J.2.4. 332 A(H1N1)pdm09 viruses were similar to the vaccine strain A/Victoria/4897/2022 and were classified as clade 6B.1A.5a.2a.1, of which 30 viruses belonged to subclade D.3.1 and 297 viruses to subclade D.3.1.1. One strain was related to the reference strain A/Sydney/5/2021 and assigned to clade 6B.1A.5a.2a, subclade C.1.9.3. 17 strain B viruses were similar to the vaccine strain B/Austria/1359417/2021 and were classified as clade V1A.3a.2, of these, 15 were assigned to subclade C.5.6, and 2 viruses were assigned to subclade C.5.6.1.

Susceptibility to antivirals. Since the beginning of the season 2025-2026, the sensitivity of 437 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) were studied in NIC (Moscow, Saint-Petersburg), including: 25 influenza A(H1N1)pdm09 viruses, 411 influenza A(H3N2) viruses and 1 influenza B virus. 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 18.6% (PCR).

In sentinel surveillance system clinical samples from 55 SARI patient were investigated by rRT-PCR for influenza, among them 2 (3.6%) cases of influenza A(H1N1)pdm09 were recognized. 1 (1.8%) of 55 SARI patients were positive for coronavirus SARS-CoV-2. Among 55 SARI samples 7 (12.7%) cases positive for ARVI were detected, including: 5 cases of RhV, 1 case of CoV and 1 case of BoV infection.

Clinical samples from 31 ILI/ARI patient were investigated by rRT-PCR for influenza, among them no positive cases were recognized. Among 31 ILI/ARI samples 9 (29.0%) cases positive for ARVI were detected, including: 1 case of PIV and 8 cases of RhV infection. Among 31 ILI/ARI samples no positive cases for coronavirus SARS-CoV-2 were recognized.

COVID-19. According to the data obtained by NIC in Saint-Petersburg totally 10537 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 was detected in 53 (0.5%) cases.

Influenza and ARI morbidity data

Fig. 1. Influenza and ARVI morbidity in 61 cities under surveillance in Russia, seasons 2025/26 and 2026/27

Morbidity 2026/27 — Fig. 1. Influenza and ARVI morbidity in 61 cities under surveillance in Russia, seasons 2025/26 and 2026/27

Epidemiological data showed decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (56.9 per 10 000 of population) was lower than national baseline (82.9) by 31.4%.

Fig. 2. Comparative data on incidence rate of clinically diagnosed influenza, seasons 2025/26 and 2026/27

Season 2026/27 — Fig. 2. Comparative data on incidence rate of clinically diagnosed influenza, seasons 2025/26 and 2026/27

Incidence rate of clinically diagnosed influenza increase comparing to previous week and amounted to 0.045 per 10 000 of population, it was lower than pre-epidemic MEM baseline (0.45).

Fig. 3. Comparison of hospitalization rate with clinical diagnosis of influenza, seasons 2025/26 and 2026/27

Hospitalization rate of clinically diagnosed influenza increased comparing to previous week and amounted to 0.013 per 10 000 of population, it was lower 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 44 RBLs and two WHO NICs. According to these data as a result of 7541 patients investigation 34 (0.5%) respiratory samples were positive for influenza, including 29 cases of influenza A(H1N1)pdm09 in 13 cities and 5 cases of influenza B in 1 city.

No influenza viruses were isolated on MDCK cell culture.

Fig. 4. Geographic distribution of RT-PCR detected influenza viruses in cities under surveillance in Russia, week 42 of 2026

Fig. 5. Monitoring of influenza viruses detection by RT-PCR in Russia, season 2026/27

H1pdm09 — Fig. 5. Monitoring of influenza viruses detection by RT-PCR in Russia, season 2026/27

Fig. 6. Monitoring of ARVI detection by RT-PCR in Russia, season 2026/27

PIV — Fig. 6. Monitoring of ARVI detection by RT-PCR in Russia, season 2026/27

ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) was estimated 18.6% of investigated samples by PCR.

Fig. 7. Monitoring of influenza viruses isolation in Russia, season 2026/27

Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 42 of 2026

	Number of specimens / number of positive cases	% positive
Influenza
Number of specimens tested for influenza	7541	-
Influenza A (not subt.)	0	0,0%
Influenza A(H1)pdm09	29	0,4%
Influenza A(H3)	0	0,0%
Influenza B	5	0,07%
All influenza	34	0,5%
Other ARVI
Number of specimens tested for ARVI	7515	-
PIV	264	3,5%
ADV	111	1,5%
RSV	9	0,1%
RhV	773	10,3%
CoV	85	1,1%
MPV	5	0,07%
BoV	153	2,0%
All ARVI	1400	18,6%
SARS-CoV-2 (COVID-19)
Number of specimens tested for SARS-CoV-2	10537	-
SARS-CoV-2	53	0,5%

Fig. 8. Results of PCR detections of SARS-CoV-2 in Russia

Table 2. Results of influenza viruses isolation in Russia, week 42 of 2026

	Number of specimens / number of viruses	% isolated viruses
Number of specimens	13	-
Influenza A(H1)pdm09	0	0,0%
Influenza A(H3)	0	0,0%
Influenza B	0	0,0%
All influenza	0	0,0%

Sentinel influenza surveillance

Clinical samples from 55 SARI patient were investigated by rRT-PCR for influenza, among them 2 (3.6%) cases of influenza A(H1N1)pdm09 were recognized. 1 (1.8%) of 55 SARI patients were positive for coronavirus SARS-CoV-2. Among 55 SARI samples 7 (12.7%) cases positive for ARVI were detected, including: 5 cases of RhV, 1 case of CoV and 1 case of BoV infection.

Fig. 9. Monitoring of influenza viruses detection by RT-PCR among SARI patients in sentinel hospitals, season 2026/27

Fig. 10. Monitoring of influenza viruses detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2026/27

Fig. 11. Monitoring of ARVI detection by RT-PCR among SARI patients in sentinel hospitals, season 2026/27

PIV — Fig. 11. Monitoring of ARVI detection by RT-PCR among SARI patients in sentinel hospitals, season 2026/27

Fig. 12. Monitoring of ARVI detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2026/27

PIV — Fig. 12. Monitoring of ARVI detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2026/27

Influenza morbidity forecasting

An influenza incidence forecast was performed. The forecast is based on the Baroyan–Rvachev model. Model calibration was carried out using data on registered influenza and acute respiratory infection (ARI) cases, as well as laboratory influenza diagnostics (PCR), from the beginning of the epidemic season (week 40) up to the week preceding the publication of the forecast. The data are presented with a one-calendar-week time step. Optimal parameters were identified using calibration algorithms, resulting in the construction of a model curve. The estimated parameters allow the model curve to be extended and a forecast to be generated for the next four weeks from the observation date (the week for which the bulletin is published).

Fig. 13. Results of influenza incidence modeling, season 2026/27.

In week 42 of 2026, a increase in incidence was observed. The situation is expected to improve in the coming weeks.

National weekly influenza bulletin of the Russian Federation

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