Epidemic Situation

Year: Week:


Week 15.04.2019-21.04.2019

Influenza and ARI morbidity data

Epidemiological data show decrease of influenza and other ARI activity in Russia in comparison with previous week. The nationwide ILI and ARI morbidity level (52.1 per 10 000 of population) became below baseline (72.2) by 27.9%.

ILI and ARI epidemic thresholds were not exeeded in all of 61 cities collaborating with two NICs of 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 2685 patients investigation 154 (5.7%) respiratory samples positive for influenza were detected including 43 (27.9%) influenza A(H1N1)pdm09 cases in 16 cities, 78 (50.6%) influenza A(H3N2) cases in 25 cities, 11 (7.1%) influenza type A cases in 3 cities and 22 (14.3%) influenza type B cases in 12 cities.

Results of influenza diagnosis
 
- No data
- No detection
- H1pdm09
- H1pdm09+H1
- H1pdm09+B
- H1pdm09+B+H1
- H1pdm09+H3
- H1pdm09+H3+H1
- H1pdm09+H3+B
- H1pdm09+H3+H1+B
- H1
- B
- B+H1
- H3
- H3+H1
- H3+B
- H3+H1+B


Influenza Virus Isolation



  - B - A(H1N1) - A(H3N2) - A(H1N1)pdm09  


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 RII98021508
(%) 0,02,01,05,10,08,2
BL of IV5605011016
(%) 0,08,90,019,60,028,6
TOTAL15407116024
(%) 0,04,50,610,40,015,6

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 RII6368212828185427166
(%) 1,30,30,24,44,42,88,54,226,1
BL of IV1260111158623
(%) 0,00,80,80,80,84,06,34,818,3
TOTAL7628322929236233189
(%) 1,00,40,33,83,83,08,14,324,8

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 RII194011 / 19400 / 049 / 17070 / 68716 / 194034 / 135075 / 146919 / 1469119 / 1506
(%) 0,6-2,90,00,82,55,11,37,9
BL of IV2412 / 2410 / 026 / 2230 / 244 / 2412 / 1417 / 1354 / 1355 / 135
(%) 0,8-11,70,01,71,45,23,03,7
TOTAL218113 / 21810 / 075 / 19300 / 71120 / 218136 / 149182 / 160423 / 1604124 / 1641
(%) 0,6-3,90,00,92,45,11,47,6

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 RII23580851111741120
(%) 0,00,32,20,50,71,75,1
BL of IV327002705234
(%) 0,00,08,30,01,50,610,4
TOTAL26850878112243154
(%) 0,00,32,90,40,81,65,7

Conclusion

Influenza and ARI incidence data. Decrease of influenza and other ARI activity was registered during the week 16.2019 in traditional surveillance system in Russia. The nationwide ILI and ARI morbidity level (52.1 per 10 000 of population) was below the national  baseline (72.2) by 27.9%.

Etiology of ILI & ARI. 154 (5.7%) respiratory samples positive for influenza were detected including 43 (27.9%) influenza A(H1N1)pdm09 cases in 16 cities, 78 (50.6%) influenza A(H3N2) cases in 25 cities, 11 (7.1%) influenza type A cases in 3 cities and 22 (14.3%) influenza type B cases in 12 cities.

Antigenic characterization. 620 influenza viruses were characterized antigenically in Moscow and Saint-Petersburg NICs including 410 influenza A(H1N1)pdm09, 191 influenza A(H3N2) and 19 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, 12 influenza A(H3N2) viruses show a 8-fold decrease HI titre with the respective strain-specific antiserum. 6 influenza B virus belonged to Victoria lineage and were antigenically related to B/Colorado/06/2017 vaccine strain and 13 influenza B viruses belonged to Yamagata lineage and were antigenically related to B/Phuket/3073/2013 reference strain.

Genetic characterizationGenetic 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 23.1% of investigated patients by IFA and 14.1% by PCR. 

In sentinel surveillance system clinical samples from 97 SARI and ILI/ARI patients were investigated by rRT-PCR.1 (2.1%) SARI case was associated with influenza B virus. Among 49 ILI/ARI patients 3 (6.1%) influenza A(H3N2)cases were recognized.