Epidemiological data show increase of influenza and other ARI activity in Russia in comparison with previous week. The ILI & ARI incidence rate (94.6 per 10 000 of population) was above by 30.3% the new nationalwide baseline (72.6) calculated by RII NIC for 2017-2018 season.
ILI and ARI epidemic thresholds were exceeded in 21 of 61 cities collaborating with two WHO NICs in Russia.
Cumulative results of influenza laboratory diagnosis by different tests were submitted by 54 RBLs and two WHO NICs. According to these data as a result of 5245 patients investigation the percent of samples positive for influenza was estimated as 27.6%. Proportion of influenza A(H1N1)pdm09, A(H3N2), type A and type B viruses was estimated as 38.4%, 24.8%, 2.6% and 34.1%, respectively.
Influenza and ARI morbidity data. Increase of influenza and other ARI activity was registered during week 11.2018 in Russia. The ILI & ARI incidence rate (94.6 per 10 000 of population) was above by 30.3% the nationalwide baseline.
Etiology of ILI & ARI morbidity. The overall percent of respiratory samples positive for influenza was estimated as 26.5%. Proportion of influenza A(H1N1)pdm09, A(H3N2), type A and type B viruses was estimated as 38.4%, 24.8%, 2.6% and 34.1%, respectively.
Antigenic characterization. 222 influenza viruses were characterized antigenically in Moscow and Saint-Petersburg NICs, including 65 influenza A(H1N1)pdm09 viruses, 44 influenza A(H3N2) strains and 113 influenza type B strains. All influenza A(H1N1)pdm09 strains were related to influenza A/Michigan/45/2015, influenza A(H3N2) strains to A/Hong Kong/4801/2014 viruses. 97 influenza type B strains belonged to Yamagata lineage and were like B/Phuket/3073/2013 reference virus, 6 influenza type B strains belonged to Victoria lineage and were antigenically related to B/Brisbain/60/2008 strain.
Genetic characterization. Full-genome NGS of 58 influenza positive samples and viruses from 6 cities was conducted. 16 influenza A(H1N1)pdm09 viruses belonged to phylogenetic group 6B.1 with amino acid substitutions in HA S84N, S162N and I216T. According to phylogenetic analisis of HA 18 of 22 tested influenza A(H3N2) viruses belonged to clade 3C.2a carring aa substitutions L3I, N144S, F159Y, K160T, N225D and Q311H in HA1. Four influenza A(H3N2) viruses belonged to genetic subgroup 3C.2a1 and carried aa substitutions K92R, N121K, T135K and H311Q. 2 influenza B viruses of Victoria-lineage belonged to genetic subgroup 1A (B/Brisbane/60/2008-like). All 18 influenza B viruses of Yamagata-lineage belonged to clade 3 (B/Phuket/3073/2013-like) and had substitution L172Q and M251V in HA1.
Susceptibility to antivirals.Most viruses were susceptible to NA inhibitors excluding three influenza A(H1N1)pdm09 strains isolated in Moscow which had H275Y amino acid substitution in NA responsible for highly reduced susceptibility to oseltamivir and zanamivir. 14 influenza strains tested in MUNANA-assay for antiviral resistance to NA inhibitors in RII NIC, including 3 A(H1N1)pdm09 strains isolated in St.Petersburg, 4 A(H3N2), two B Victoria strains and 5 B Yamagata viruses were susceptible to oseltamivir and zanamivir. All influenza A strains tested were resistant to rimantadine.
Percent of positive ARI cases of non-influenza etiology (PIV, adeno- and RSV) was estimated as 18.3% of investigated patients by IFA and 8.3% by PCR. Last weeks RSV dominated among ARI agents.
In sentinel surveillance system clinical samples from 144 SARI and ILI/ARI patients were investigated by rRT-PCR. 35 (44.3%) influenza cases were detected among SARI patients, including 8 influenza A(H1N1)pdm09 cases, 16 influenza A(H3N2) cases and 11 influenza B cases. Among ILI/ARI patients 20 (30.8%) influenza cases were detected, including 4 influenza A(H1N1)pdm09, 8 influenza A(H3N2) and 8 influenza B cases.
