Introduction. The surveillance of influenza viruses in ARVI structure and study of their properties in epidemic season 2019–2020 in Russian Federation are actual for investigations due to tasks of Global Influenza Strategy initiated by WHO in 2019.Material and methods. The data of epidemiological surveillance on influenza- and ARVI-associated morbidity and hospitalization in different age groups of population were analyzed; virological, genetic and statistical methods were used.Results. Preschool children were involved in epidemic the most. Meanwhile, the highest rate of hospitalization was observed in patients of 18–40 years old. Influenza A(H1N1)pdm09 virus dominated in etiology of ARVI in hospitalized patients and pneumonia. The role of respiratory viruses in severe cases of pneumonia and bronchoalveolar syndrome in children was shown. The differences in spectrum of circulating viruses caused ARVI in different regions of Russia were found. Influenza A(H1N1)pdm09 and B/Victoria-like viruses were the main etiological agents that caused of epidemic; its activity among all ARVI was 7.3 and 8.0%, respectively. The differences in antigenic properties of influenza A(H3N2) and B epidemic strains compared to vaccine viruses were found. The populations of epidemic strains were presented by following dominant genetic groups: 6B1.A5/183P for A(H1N1)pdm09, 3С.2а1b+137F for A(H3N2) and V1A.3 line B/Victoria-like for B viruses. The good profile of epidemic strains susceptibility to anti-neuraminidase inhibitors has been saved. The most of the studied influenza strains had the receptor specificity characteristic of human influenza viruses.Conclusions. Obtained results identified the peculiarities of viruses caused the influenza and ARVI in epidemic season 2019–2020 in different regions of Russia. These results suggested the important role of influenza A(H1N1) pdm09 in severe cases and pneumonia in adults 18–40 years old. The continuing drift in influenza viruses was found, which, apparently, could not but affect the efficacy of vaccine prophylaxis and was also considered in the recommendations of WHO experts on the composition of influenza vaccines for the countries of the Northern Hemisphere in the 2020–2021 season.
Background
To better understand the impact of seasonal influenza in pregnant women we analyzed data collected during four seasons at a hospital for acute respiratory infection that specializes in treating pregnant women.
Methods
This was a single-center active surveillance study of women 15–44 years of age hospitalized for acute respiratory diseases between 2012/2013 and 2015/2016 in Moscow, Russian Federation. Women had to have been hospitalized within 7 days of the onset of symptoms. Swabs were taken within 48 h of admission, and influenza was detected by reverse transcription-polymerase chain reaction.
Results
During the four seasons, of the 1992 hospitalized women 1748 were pregnant. Laboratory-confirmed influenza was detected more frequently in pregnant women (825/1748; 47.2%) than non-pregnant women (58/244; 23.8%) (OR for influenza = 2.87 [95% CI, 2.10–3.92];
p
< 0.001). This pattern was homogenous across seasons (
p
= 0.112 by test of homogeneity of equal odds). Influenza A(H1N1)pdm09 was the dominant strain in 2012/2013, A(H3N2) in 2013/2014, B/Yamagata lineage and A(H3N2) in 2014/2015, and A(H1N1)pdm09 in 2015/2016. Influenza-positive pregnant admissions went to the hospital sooner than influenza-negative pregnant admissions (
p
< 0.001). The risk of influenza increased by 2% with each year of age and was higher in women with underlying conditions (OR = 1.52 [95% CI, 1.16 to 1.99]). Pregnant women positive for influenza were homogeneously distributed by trimester (
p
= 0.37 for homogeneity;
p
= 0.49 for trend). Frequencies of stillbirth, delivery, preterm delivery, and caesarean delivery did not significantly differ between influenza-positive and influenza-negative hospitalized pregnant women or between subtypes/lineages.
Conclusions
Pregnant women are at increased risk for hospitalization due to influenza irrespective of season, circulating viruses, or trimester.
Electronic supplementary material
The online version of this article (10.1186/s12884-019-2192-z) contains supplementary material, which is available to authorized users.
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