Epidemiological data show decrease of influenza and other ARI activity in Russia in comparison with previous week. The ILI & ARI incidence rate (70.0 per 10 000 of population) was below by 3.6% the new nationalwide baseline (72.6) calculated by RII NIC for 2017-2018 season.
ILI and ARI epidemic thresholds were exceeded in 5 of 61 cities collaborating with two WHO NICs in Russia.
Exceeding of morbidity epidemic thresholds for overall population
- No data
- less 20%
- 20 - 49%
- 50% and more
Cumulative number of diagnosed influenza cases
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 3523 patients investigation the percent of 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 40.3%, 26.4%, 5.2% and 28.1%, respectively.
Results of influenza diagnosis
- No data
- No detection
- H1pdm09
- H1pdm09+H1
- H1pdm09+B
- H1pdm09+B+H1
Influenza Virus Antigen Detection by Immunofluorescence Assay (IFA)
- B
- A(H1N1) + A(H1N1)pdm09
- A(H3N2)
- PIV
- AD
- RS
Influenza Virus RNA Detection by RT-PCR
- B
- A(H1N1)
- A(H3N2)
- A(H1N1)pdm09
- PIV
- AD
- RS
Table 1.
Influenza Virus Isolation
Base lab.
Number of investigated patients
Number of viruses isolated
H1
H3
B
H1pdm09
Untyped virus
Total
BL of RII
228
0
17
20
15
0
52
(%)
0,0
7,5
8,8
6,6
0,0
22,8
BL of IV
143
0
17
14
11
0
42
(%)
0,0
11,9
9,8
7,7
0,0
29,4
TOTAL
371
0
34
34
26
0
94
(%)
0,0
9,2
9,2
7,0
0,0
25,3
Table 2.
Influenza Virus Antigen Detection by Immunofluorescence Assay (IFA)
Base lab.
Number of investigated patients
Influenza
Parainfluenza
AD
RS
Total
H1+H1pdm09
H3
B
I
II
III
BL of RII
767
40
38
13
18
8
25
28
36
206
(%)
5,2
5,0
1,7
2,3
1,0
3,3
3,7
4,7
26,9
BL of IV
106
2
2
3
3
2
7
8
14
41
(%)
1,9
1,9
2,8
2,8
1,9
6,6
7,5
13,2
38,7
TOTAL
873
42
40
16
21
10
32
36
50
247
(%)
4,8
4,6
1,8
2,4
1,1
3,7
4,1
5,7
28,3
Table 3.
Influenza Virus RNA Detection by RT-PCR
Base lab.
Number of investigated patients
Influenza
PIV
AD
RS
A (not subtyped)
H1
H3
H5
B
H1pdm09
BL of RII
2466
48 / 2432
0 / 722
158 / 2233
0 / 650
211 / 2462
293 / 2324
18 / 1413
49 / 1439
109 / 1440
(%)
2,0
0,0
7,1
0,0
8,6
12,6
1,3
3,4
7,6
BL of IV
419
1 / 419
0 / 59
36 / 363
0 / 59
32 / 419
45 / 332
1 / 224
2 / 224
13 / 224
(%)
0,2
0,0
9,9
0,0
7,6
13,6
0,4
0,9
5,8
TOTAL
2885
49 / 2851
0 / 781
194 / 2596
0 / 709
243 / 2881
338 / 2656
19 / 1637
51 / 1663
122 / 1664
(%)
1,7
0,0
7,5
0,0
8,4
12,7
1,2
3,1
7,3
Table 4.
Cumulative number of diagnosed influenza cases
Base lab.
Number of investigated patients
Number of diagnosed influenza cases
H1
H1+H1pdm09 (IFA)
H3
A (not subtyped)
B
H1pdm09
Total
BL of RII
3025
0
40
211
48
228
331
818
(%)
0,0
1,3
7,0
1,6
7,5
10,9
27,0
BL of IV
498
0
2
36
1
34
45
116
(%)
0,0
0,4
7,2
0,2
6,8
9,0
23,3
TOTAL
3523
0
42
247
49
262
376
934
(%)
0,0
1,2
7,0
1,4
7,4
10,7
26,5
Conclusion
Influenza and ARI morbidity data. Decrease of influenza and other ARI activity was registered during week 10.2018 in Russia. The ILI & ARI incidence rate (70.0 per 10 000 of population) was below by 3.6% 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 40.3%, 26.4%, 5.2% and 28.1%, respectively.
Antigenic characterization. 180 influenza viruses were characterized antigenically in Moscow and Saint-Petersburg NICs, including 47 influenza A(H1N1)pdm09 viruses, 41 influenza A(H3N2) strains and 92 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. 86 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 17.0% of investigated patients by IFA and 11.6% by PCR. Last weeks RSV dominated among ARI agents.
In sentinel surveillance system clinical samples from 93 SARI and ILI/ARI patients were investigated by rRT-PCR.16 (40.0%) influenza cases were detected among SARI patients, including 6 influenza A(H1N1)pdm09 cases, 4 influenza A(H3N2) cases and 6 influenza B cases. Among ILI/ARI patients 13 (24.5%) influenza cases were detected, including 6 influenza A(H1N1)pdm09, 6 influenza A(H3N2) and 1 influenza B case.