National Weekly Bulletin

NATIONAL WEEKLY INFLUENZA BULLETIN OF THE RUSSIAN FEDERATION

week 1 of 2023 (02.01.23 - 08.01.23)

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 (53.0 per 10 000 of population) was lower than national baseline (70.0) by 24.3%.

Etiology of ILI & ARI. Among 4147 investigation patients in 40 cities 1246 (30.0%) respiratory samples were positive for influenza, including 917 cases of influenza A(H1N1)pdm09 in 32 cities, 4 cases of influenza A(H3N2) in 2 cities, 139 cases of influenza A unsubtyped in 7 cities and 186 cases of influenza B in 25 cities.

No influenza viruses were isolated on MDCK cell culture. Since the beginning of the season, 286 viruses A(H1N1)pdm09, 5 viruses A(H3N2) and 29 viruses B have been isolated.

Antigenic characterization. Since the beginning of the season, 89 influenza A(H1N1)pdm09 have been antigenically characterized by the NICs, including: Moscow (37) and Saint-Petersburg (52), 2 influenza A(H3N2) in Saint-Petersburg and 18 influenza B, including: Moscow (5) and Saint-Petersburg (13). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. All A(H3N2) strains were similar to the reference virus A/Darwin/9/2021. 12 influenza B viruses were antigenically similar to reference strain В/Austria/1359417/2021 and 1 influenza B virus reacted with the reference virus antiserum to a 1:8 homologous titer.

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 9.4% (PCR).

In sentinel surveillance system clinical samples from 21 SARI patients were investigated by rRT-PCR for influenza, among them 2 (9.5%) cases of influenza A(H1N1)pdm09 were detected. Among 10 SARI patients one case of ARVI recognized. Among 10 SARI patients no cases positive for coronavirus SARS-CoV-2 recocognized.

Clinical samples from 13 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 2 (15.4%) cases of influenza A(H1N1)pdm09  were detected. Among 8 ILI/ARI samples one case of ARVI recognized. No of 8 ILI/ARI patients were positive for coronavirus SARS-CoV-2.

COVID-19. Totally 21 841 644 cases and 394 262 deaths associated with COVID-19 were registered in Russia including 4 675 cases and 48 deaths in last 24 hours (on 12:00 of 12.01.2023). According to the data obtained by NIC in Saint-Petersburg totally 5 772 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 294 (5.1%) cases.

Influenza and ARI morbidity data

Epidemiological data showed decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (53.0 per 10 000 of population) was lower than national baseline (70.0) by 24.3%.

Incidence rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.75 per 10 000 of population, it was higer than pre-epidemic MEM baseline (0.060).

Hospitalization rate of clinically diagnosed influenza decreased comparing to previous week and amounted to 0.40 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 40 RBLs and two WHO NICs. According to these data as a result of 4147 patients investigation 1246 (30.0%) respiratory samples were positive for influenza, including 917 cases of influenza A(H1N1)pdm09 in 32 cities, 4 cases of influenza A(H3N2) in 2 cities, 139 cases of influenza A unsubtyped in 7 cities and 186 cases of influenza B in 25 cities.

No influenza viruses were isolated on MDCK cell culture. Since the beginning of the season 388 viruses A(H1N1)pdm09, 11 viruses A(H3N2) and 41 viruses B have been isolated.

Antigenic characterization. Since the beginning of the season, 89 influenza A(H1N1)pdm09 have been antigenically characterized by the NICs, including: Moscow (37) and Saint-Petersburg (52), 2 influenza A(H3N2) in Saint-Petersburg and 18 influenza B, including: Moscow (5) and Saint-Petersburg (13). All viruses A(H1N1)pdm09 were antigenically similar to reference strain A/Victoria/2570/2019 (H1N1)pdm09. All A(H3N2) strains were similar to the reference virus A/Darwin/9/2021. 12 influenza B viruses were antigenically similar to reference strain В/Austria/1359417/2021 and 1 influenza B virus reacted with the reference virus antiserum to a 1:8 homologous titer.

ARVI detections. The overall proportion of respiratory samples tested positive for other ARVI (PIV, ADV, RSV, RhV, CoV, MPV, BoV) estimated as 9.4% of investigated samples by PCR.

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

COVID-19. Totally 21 841 644 cases and 394 262 deaths associated with COVID-19 were registered in Russia including 4 675 cases and 48 deaths in last 24 hours (on 12:00 of 12.01.2023). According to the data obtained by NIC in Saint-Petersburg totally 5 772 clinical samples were PCR investigated in last week. Among them coronavirus SARS-CoV-2 detected in 294 (5.1%) cases.

Table 2. Results of influenza viruses isolation in Russia, week 1 of 2023

Sentinel influenza surveillance

Clinical samples from 21 SARI patients were investigated by rRT-PCR for influenza, among them 2 (9.5%) cases of influenza A(H1N1)pdm09 were detected. Among 10 SARI patients one case of ARVI recognized. Among 10 SARI patients no cases positive for coronavirus SARS-CoV-2 recocognized.

Clinical samples from 13 ILI/ARI patients were investigated for influenza by rRT-PCR, among them 2 (15.4%) cases of influenza A(H1N1)pdm09  were detected. Among 8 ILI/ARI samples one case of ARVI recognized. No of 8 ILI/ARI patients were positive for coronavirus SARS-CoV-2.