Epidemic Situation

Year: Week:


Week 04.03.2019-10.03.2019

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 (66.1 per 10 000 of population) was below then national baseline (72.2) by 8.4%.

ILI and ARI epidemic thresholds were exeeded in 4 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 53 RBLs and two WHO NICs. According to these data as a result of 5124 patients investigation 1356 (26.5%) respiratory samples positive for influenza were detected including 588 influenza A(H1N1)pdm09 cases in 49 cities, 593 influenza A(H3N2) cases in 46 cities, 153 influenza type A cases in 7 cities and 22 influenza type B cases in 8 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 RII175015040055
(%) 0,08,60,022,90,031,4
BL of IV137018015033
(%) 0,013,10,010,90,024,1
TOTAL312033055088
(%) 0,010,60,017,60,028,2

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 RII909263522861246335274
(%) 2,93,90,23,16,72,66,93,930,1
BL of IV12278023145544
(%) 5,76,60,01,62,511,54,14,136,1
TOTAL1031334323064386840318
(%) 3,24,20,22,96,23,76,63,930,8

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 RII4020141 / 40200 / 0514 / 40190 / 175415 / 4020509 / 401928 / 257622 / 262890 / 2618
(%) 3,5-12,80,00,412,71,10,83,4
BL of IV43812 / 4380 / 049 / 4180 / 1015 / 43851 / 4385 / 2525 / 2528 / 252
(%) 2,7-11,70,01,111,62,02,03,2
TOTAL4458153 / 44580 / 0563 / 44370 / 185520 / 4458560 / 445733 / 282827 / 288098 / 2870
(%) 3,4-12,70,00,412,61,20,93,4

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 RII4633026540141175351233
(%) 0,00,611,73,00,411,526,6
BL of IV491075312553123
(%) 0,01,410,82,41,010,825,1
TOTAL5124033593153225881356
(%) 0,00,611,63,00,411,526,5

Conclusion

Influenza and ARI morbidity data. Decreased influenza and other ARI activity was registered during the week 10.2019 in traditional surveillance system in Russia. The nationwide ILI and ARI morbidity level (66.1 per 10 000 of population) was below then national baseline (72.2) by 8.4%.

Etiology of ILI & ARI morbidity. 1356 (26.5%) respiratory samples positive for influenza were detected including 588 influenza A(H1N1)pdm09 cases in 49 cities, 593 influenza A(H3N2) cases in 46 cities, 153 influenza type A cases in 7 cities and 22 influenza type B cases in 8 cities.

Antigenic characterization. 369 influenza viruses were characterized antigenically in Moscow and Saint-Petersburg NICs including 258 influenza A(H1N1)pdm09, 103 influenza A(H3N2) strains and 8 influenza type B strain. All influenza A(H1N1)pdm09 viruses were related to influenza A/Michigan/45/2015 vaccine strain, 100 influenza A(H3N2) viruses were like to A/Singapure/INFIMN-16-0019/2016 vaccine strain, 3 influenza A(H3N2) viruses were antigenically different from a reference virus and had to show a decrease of 8-fold HI titre with the respective post-infection antiserum. 3 influenza B virus belonged to Victoria lineage and antigenically related to B/Colorado/06/2017 vaccine strain and 3 influenza B viruses were belonged to Yamagata lineage and related to B/Phuket/3073/2013 reference strain.

Genetic characterizationGenetic analysis of 101 influenza viruses HA from isolate and clinical samples including 58 influenza A(H1N1)pdm09 strains, 42 influenza A(H3N2) strains and 1 influenza type B virus were performed. All A(H1N1)pdm09 viruses were like to the vaccine strain A/Michigan/45/2015 (6B.1clade). All A(H3N2) viruses were like A/ALsace/1746/2018 reference strain (3C.2a1b subgroup). Influenza B strain of Victoria lineage belonged to subclade V1A.1 with two amino acid deletion (162-163) in HA molecule.

Susceptibility to antivirals. All influenza A viruses were susceptible to oseltamivir. One influenza B/Arkhangelsk/RII-01/2018 virus had reduced susceptibility to oseltamivir.

Percent of positive ARI cases of non-influenza etiology (PIV, adeno- and RSV) was estimated as 23.3% of investigated patients by IFA and 11.9% by PCR. 

In sentinel surveillance system clinical samples from 79 SARI and ILI/ARI patients were investigated by rRT-PCR. 14 (45.2%) SARI cases were associated with influenza, including 8 influenza A(H1N1)pdm09 cases and 6 A(H3N2) cases. Among 48 ILI/ARI patients 13 (27.1%) influenza cases were recognized, including 11 influenza A(H1N11)pdm09 cases and 2 A(H3N2) cases.