Epidemiological data show decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (30.7 per 10 000 of population) became below baseline (72.2) by 57.5%.
ILI and ARI epidemic thresholds were not exeeded in all of 61 cities collaborating with two NICs of Russia.
Cumulative results of influenza laboratory diagnosis by different tests were submitted by 49 RBLs and two WHO NICs. According to these data as a result of 1287 patients investigation 44 (3.4%) respiratory samples positive for influenza were detected including 13 (29.5%) influenza A(H1N1)pdm09 cases in 10 cities, 18 (40.9%) influenza A(H3N2) cases in 8 cities, 2 (4.5%) influenza type A cases in 1 city and 11 (25.0%) influenza type B cases in 8 cities.
Influenza and ARI incidence data. Decrease of influenza and other ARI activity was registered during the week 19.2019 in traditional surveillance system in Russia. The nationwide ILI and ARI morbidity level (30.7 per 10 000 of population) became below baseline (72.2) by 57.5%.
Etiology of ILI & ARI. 44 (3.4%) respiratory samples positive for influenza were detected including 13 (29.5%) influenza A(H1N1)pdm09 cases in 10 cities, 18 (40.9%) influenza A(H3N2) cases in 8 cities, 2 (4.5%) influenza type A cases in 1 city and 11 (25.0%) influenza type B cases in 8 cities.
Antigenic characterization. 655 influenza viruses were characterized antigenically in Moscow and Saint-Petersburg NICs including 436 influenza A(H1N1)pdm09, 197 influenza A(H3N2) and 22 influenza type B strains. All influenza A(H1N1)pdm09 viruses were related to influenza A/Michigan/45/2015 vaccine strain, 137 influenza A(H3N2) viruses were like to A/Singapure/INFIMH-16-0019/2016 vaccine strain, 18 influenza A(H3N2) viruses show a 8-fold decrease HI titre with the respective strain-specific antiserum. 8 influenza B virus belonged to Victoria lineage and were antigenically related to B/Colorado/06/2017 vaccine strain and 14 influenza B viruses belonged to Yamagata lineage and were antigenically related to B/Phuket/3073/2013 reference strain.
Genetic characterization. Genetic analysis of 211 influenza viruses HA from isolate and clinical samples including 107 influenza A(H1N1)pdm09 strains, 98 influenza A(H3N2) strains and 6 influenza B virus were performed. All influenza A(H1N1)pdm09 viruses were like to the vaccine strain A/Michigan/45/2015 (6B.1clade). All influenza A(H3N2) viruses were like A/Alsace/1746/2018 reference strain (3C.2a1b subgroup). Two influenza B strains of Victoria lineage belonged to subclade V1A.1 with two amino acid deletion (162-163) in HA molecule, 4 influenza B strains belonged to Yamagata lineage clade 3.
Susceptibility to antivirals. All influenza A viruses were susceptible to oseltamivir. One influenza B/Arkhangelsk/RII-01/2018 virus had reduced susceptibility to oseltamivir.
Percentage of positive ARI cases of non-influenza etiology (PIV, adeno- and RSV) was estimated as 21.8% of investigated patients by IFA and 11.2% by PCR.
In sentinel surveillance system clinical samples from 40 SARI and ILI/ARI patients were investigated by rRT-PCR. 1 (3.3%) SARI case was associated with influenza A(H3N2) virus. Among 10ILI/ARI patients no influenza cases were recognized.
