Epidemic Situation

Year: Week:

NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 8 of 2023 (20.02.23 - 26.02.23)

Summary

Influenza and ARI incidence data. Influenza and other ARI activity decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (67.2 per 10 000 of population) was higer than national baseline (70.0) by 4.0%.

Etiology of ILI & ARI. Among 7410 patients investigation 746 (10.1%) respiratory samples were positive for influenza, including 27 cases of influenza A(H1N1)pdm09 in 12 cities, 5 cases of influenza A(H3N2) in 2 cities, 29 cases of influenza A unsubtyped in 7 cities and 685 cases of influenza B in 44 cities.

30 influenza viruses were isolated on MDCK cell culture, including: 13 influenza A(H1N1)pdm09 viruses in Kaliningrad (1), Krasnoyarsk (6), Moscow (2), Omsk (4); 1 influenza A(H3N2) virus in Saint-Petersburg; 16 influenza B viruses in Astrakhan (1), Vladivostok (5), Novosibirsk (1), Omsk (1), St. Petersburg (3), Tomsk (1), Khabarovsk (4). Since the beginning of the season 930 influenza viruses were isolated on MDCK cell culture, including: 678 viruses A(H1N1)pdm09, 20 viruses A(H3N2) and 232 viruses B.

Antigenic characterization. Since the beginning of the season, 414 influenza A(H1N1)pdm09 viruses have been antigenically characterized by the NICs, including: Moscow (81) and Saint-Petersburg (333), 24 influenza A(H3N2) viruses in Saint-Petersburg and 86 influenza B, including: Moscow (7) and Saint-Petersburg (79). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. 22 influenza A(H3N2) strains were similar to the reference virus A/Darwin/9/2021 and 2 influenza A(H3N2) viruses reacted with the reference virus antiserum to a 1:8 homologous titer. 66 influenza B viruses were antigenically similar to reference strain /Austria/1359417/2021 and 2 influenza B viruses reacted with the reference virus antiserum to a 1:8 homologous titer.

Genetic analysis. Sequencing of 993 influenza viruses and isolates from primary clinical materials from patients was performed by the NIC (Saint-Petersburg). According to phylogenetic analysis, 904 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; 27 A(H3N2) viruses was assigned to subgroup 3C.2 a1b.2a.2 and similar to reference virus Bangladesh/4005/2020 (H3N2); 62 influenza type B viruses were assigned to genetic subgroup V1A.3a.2 reference virus B/Austria/1359417/2021..Susceptibility to antivirals. The sensitivity of 280 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in two NICs (Moscow, St. Petersburg), including 224 A(H1N1)pdm09 viruses and 6 A(H3N2) viruses in NIC (Saint-Petersburg) and 45 A(H1N1)pdm09 viruses and 5 B viruses in NIC (Moscow). All the viruses studied were sensitive 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 11.2% (PCR).

In sentinel surveillance system clinical samples from 36 SARI patients were investigated by rRT-PCR for influenza, among them 9 (25.0%) cases of influenza B. Among 26 SARI samples 4 (15.4%) cases positive for ARVI detected including 1 case of ADV, 2 cases of RSV and 1 case of RhV infection. Among 36 SARI patients no cases positive for coronavirus SARS-CoV-2 recocognized. 

Clinical samples from 56 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 4 (7.1%) cases of influenza B. Among 48 ILI/ARI samples 10 (20.8%) cases positive for ARVI detected including 6 cases of RhV, 3 cases of CoV and 1 case of MPV infection. 7 (12.5%) of 56 ILI/ARI patients were positive for coronavirus SARS-CoV-2.  

COVID-19. Totally 22 300 004 cases and 396 176 deaths associated with COVID-19 were registered in Russia including 14 096 cases and 39 deaths in last 24 hours (on 12:00 of 02.03.2023). According to the data obtained by NIC in Saint-Petersburg totally 10 790 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 1492 (13.8%) cases.

Influenza and ARI morbidity data

Fig. 1. Influenza and ARVI morbidity in 61 cities under surveillance in Russia, seasons 2021/22 and 2022/23
Rates per 10 000 populationFig. 1. Influenza and ARVI morbidity in 61 cities under surveillance in Russia, seasons 2021/22 and 2022/23

Weeks

  • Morbidity 2022/23Morbidity 2022/23
  • Morbidity 2021/22Morbidity 2021/22
  • MEM baseline 2022/23MEM baseline 2022/23

Epidemiological data showed decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (67.2 per 10 000 of population) was higer than national baseline (70.0) by 4.0%.

Fig. 2. Comparative data on incidence rate of clinically diagnosed influenza, seasons 2021/22 and 2022/23
Rates per 10 000 populationFig. 2. Comparative data on incidence rate of clinically diagnosed influenza, seasons 2021/22 and 2022/23

Weeks

  • Season 2022/23Season 2022/23
  • Season 2021/22Season 2021/22
  • MEM baselineMEM baseline

Incidence rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.61 per 10 000 of population, it was higer than pre-epidemic MEM baseline (0.060).

Fig. 3. Comparison of hospitalization rate with clinical diagnosis of influenza, seasons 2021/22 and 2022/23
Rates per 10 000 populationFig. 3. Comparison of hospitalization rate with clinical diagnosis of influenza, seasons 2021/22 and 2022/23

Weeks

  • Season 2022/23Season 2022/23
  • Season 2021/22Season 2021/22
  • MEM baselineMEM baseline

Hospitalization rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.14 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 48 RBLs and two WHO NICs. According to these data as a result of 7410 patients investigation 746 (10.1%) respiratory samples were positive for influenza, including 27 cases of influenza A(H1N1)pdm09 in 12 cities, 5 cases of influenza A(H3N2) in 2 cities, 29 cases of influenza A unsubtyped in 7 cities and 685 cases of influenza B in 44 cities.

30 influenza viruses were isolated on MDCK cell culture, including: 13 influenza A(H1N1)pdm09 viruses in Kaliningrad (1), Krasnoyarsk (6), Moscow (2), Omsk (4); 1 influenza A(H3N2) virus in Saint-Petersburg; 16 influenza B viruses in Astrakhan (1), Vladivostok (5), Novosibirsk (1), Omsk (1), St. Petersburg (3), Tomsk (1), Khabarovsk (4). Since the beginning of the season 930 influenza viruses were isolated on MDCK cell culture, including: 678 viruses A(H1N1)pdm09, 20 viruses A(H3N2) and 232 viruses B.

Antigenic characterization. Since the beginning of the season, 414 influenza A(H1N1)pdm09 viruses have been antigenically characterized by the NICs, including: Moscow (81) and Saint-Petersburg (333), 24 influenza A(H3N2) viruses in Saint-Petersburg and 86 influenza B, including: Moscow (7) and Saint-Petersburg (79). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. 22 influenza A(H3N2) strains were similar to the reference virus A/Darwin/9/2021 and 2 influenza A(H3N2) viruses reacted with the reference virus antiserum to a 1:8 homologous titer. 66 influenza B viruses were antigenically similar to reference strain /Austria/1359417/2021 and 2 influenza B viruses reacted with the reference virus antiserum to a 1:8 homologous titer.Genetic analysis. Sequencing of 993 influenza viruses and isolates from primary clinical materials from patients was performed by  NIC (Saint-Petersburg). According to phylogenetic analysis, 904 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; 27 A(H3N2) viruses was assigned to subgroup 3C.2 a1b.2a.2 and similar to reference virus Bangladesh/4005/2020 (H3N2); 62 influenza type B viruses were assigned to genetic subgroup V1A.3a.2 reference virus B/Austria/1359417/2021.Susceptibility to antivirals. The sensitivity of 280 influenza viruses to neuraminidase inhibitors (oseltamivir, zanamivir) was studied in two NICs (Moscow, St. Petersburg), including 224 A(H1N1)pdm09 viruses and 6 A(H3N2) viruses in NIC (Saint-Petersburg) and 45 A(H1N1)pdm09 viruses and 5 B viruses in NIC (Moscow). All the viruses studied were sensitive to oseltamivir and zanamivir.

Fig. 4. Geographic distribution of RT-PCR detected influenza viruses in cities under surveillance in Russia, week 8 of 2023
Fig. 4. Geographic distribution of RT-PCR detected influenza viruses in cities under surveillance in Russia, week 8 of 2023
PCR results
  • No dataNo data
  • No viruses detectedNo viruses detected
  • H1pdm09H1pdm09
  • H3H3
  • H3+H1pdm09H3+H1pdm09
  • BB
  • B+H1pdm09B+H1pdm09
  • B+H3B+H3
  • B+H3+H1pdm09B+H3+H1pdm09
  • A (not subt.)A (not subt.)
  • A (not subt.)+H1pdm09A (not subt.)+H1pdm09
  • A (not subt.)+H3A (not subt.)+H3
  • A (not subt.)+H3+H1pdm09A (not subt.)+H3+H1pdm09
  • A (not subt.)+BA (not subt.)+B
  • A (not subt.)+B+H1pdm09A (not subt.)+B+H1pdm09
  • A (not subt.)+B+H3A (not subt.)+B+H3
  • A (not subt.)+B+H3+H1pdm09A (not subt.)+B+H3+H1pdm09
Fig. 5. Monitoring of influenza viruses detection by RT-PCR in Russia, season 2022/23
Number of positive casesFig. 5. Monitoring of influenza viruses detection by RT-PCR in Russia, season 2022/23% positive

Weeks

  • H1pdm09H1pdm09
  • H3H3
  • BB
  • A (not subt.)A (not subt.)
  • % positive% positive
Fig. 6. Monitoring of ARVI detection by RT-PCR in Russia, season 2022/23
Number of positive casesFig. 6. Monitoring of ARVI detection by RT-PCR in Russia, season 2022/23

Weeks

  • PIVPIV
  • ADVADV
  • RSVRSV
  • RhVRhV
  • CoVCoV
  • MPVMPV
  • BoVBoV

ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) estimated as 11.2% of investigated samples by PCR.

Fig. 7. Monitoring of influenza viruses isolation in Russia, season 2022/23
Number of positive casesFig. 7. Monitoring of influenza viruses isolation in Russia, season 2022/23% positive

Weeks

  • H1pdm09H1pdm09
  • H3H3
  • BB
  • % positive% positive

Table 1. Results of influenza and other ARVI detection by RT-PCR in Russia, week 8 of 2023

  Number of  specimens / number of positive cases  % positive
Influenza
Number of specimens tested for influenza 7410 -
Influenza A (not subt.) 29 0,4%
Influenza A(H1)pdm09 27 0,4% 
Influenza A(H3) 5 0,07% 
Influenza B 685 9,2% 
All influenza 746 10,1%
Other ARVI
Number of specimens tested for ARVI 6808  -
PIV 32 0,5%
ADV 78 1,1%
RSV 226 3,3%
RhV 222 3,3%
CoV 118 1,7%
MPV 62 0,9%
BoV 25 0,4%
All ARVI 763 11,2%
SARS-CoV-2 (COVID-19)
Number of specimens tested for SARS-CoV-2 10790 -
SARS-CoV-2 1492 13,8%
Fig. 8. Results of PCR detections of SARS-CoV-2 in Russia
Fig. 8. Results of PCR detections of SARS-CoV-2 in Russia
% positive
  • No dataNo data
  • less then 10%less then 10%
  • 10-20%10-20%
  • 20-30%20-30%
  • 30-40%30-40%
  • 40-50%40-50%
  • 50% and more50% and more

COVID-19. Totally 22 300 004 cases and 396 176 deaths associated with COVID-19 were registered in Russia including 14 096 cases and 39 deaths in last 24 hours (on 12:00 of 02.03.2023). According to the data obtained by NIC in Saint-Petersburg totally 10 790 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 1492 (13.8%) cases.

Table 2. Results of influenza viruses isolation in Russia, week 8 of 2023

  Number of specimens / number of viruses  % isolated viruses
Number of specimens 112 -
Influenza A(H1)pdm09 13 11,6% 
Influenza A(H3) 1 0,9% 
Influenza B 16 14,3% 
All influenza 30 26,8%

Sentinel influenza surveillance

linical samples from 36 SARI patients were investigated by rRT-PCR for influenza, among them 9 (25.0%) cases of influenza B. Among 26 SARI samples 4 (15.4%) cases positive for ARVI detected including 1 case of ADV, 2 cases of RSV and 1 case of RhV infection. Among 36 SARI patients no cases positive for coronavirus SARS-CoV-2 recocognized. 

Clinical samples from 56 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 4 (7.1%) cases of influenza B. Among 48 ILI/ARI samples 10 (20.8%) cases positive for ARVI detected including 6 cases of RhV, 3 cases of CoV and 1 case of MPV infection. 7 (12.5%) of 56 ILI/ARI patients were positive for coronavirus SARS-CoV-2. 

Fig. 9. Monitoring of influenza viruses detection by RT-PCR among SARI patients in sentinel hospitals, season 2022/23
Number of positive casesFig. 9.  Monitoring of influenza viruses detection by RT-PCR among SARI patients in sentinel hospitals, season 2022/23% positive

Weeks

  • H1pdm09H1pdm09
  • H3H3
  • BB
  • A (not subt.)A (not subt.)
  • % positive% positive
Fig. 10. Monitoring of influenza viruses detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2022/23
Number of positive casesFig. 10.  Monitoring of influenza viruses detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2022/23% positive

Weeks

  • H1pdm09H1pdm09
  • H3H3
  • BB
  • A (not subt.)A (not subt.)
  • % positive% positive
Fig. 11. Monitoring of ARVI detection by RT-PCR among SARI patients in sentinel hospitals, season 2022/23
Number of positive casesFig. 11.  Monitoring of ARVI detection by RT-PCR among SARI patients in sentinel hospitals, season 2022/23

Weeks

  • PIVPIV
  • ADVADV
  • RSVRSV
  • RhVRhV
  • CoVCoV
  • MPVMPV
  • BoVBoV
Fig. 12. Monitoring of ARVI detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2022/23
Number of positive casesFig. 12.  Monitoring of ARVI detection by RT-PCR among ILI/ARI patients in sentinel polyclinics, season 2022/23

Weeks

  • PIVPIV
  • ADVADV
  • RSVRSV
  • RhVRhV
  • CoVCoV
  • MPVMPV
  • BoVBoV
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