Reciprocal circulation pattern of SARS-CoV-2 and influenza viruses during the influenza seasons 2019/2020 and 2020/2021 in the Bavarian Influenza Sentinel (Germany)

Abstract

The corona virus disease-2019 (COVID-19) pandemic began in Wuhan, China, and quickly spread around the world. The pandemic overlapped with two consecutive influenza seasons (2019/2020 and 2020/2021). This provided the opportunity to study community circulation of influenza viruses and severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) in outpatients with acute respiratory infections during these two seasons within the Bavarian Influenza Sentinel (BIS) in Bavaria, Germany. From September to March, oropharyngeal swabs collected at BIS were analysed for influenza viruses and SARS-CoV-2 by real-time polymerase chain reaction. In BIS 2019/2020, 1376 swabs were tested for influenza viruses. The average positive rate was 37.6%, with a maximum of over 60% (in January). The predominant influenza viruses were Influenza A(H1N1)pdm09 (n = 202), Influenza A(H3N2) (n = 144) and Influenza B Victoria lineage (n = 129). In all, 610 of these BIS swabs contained sufficient material to retrospectively test for SARS-CoV-2. SARS-CoV-2 RNA was not detectable in any of these swabs. In BIS 2020/2021, 470 swabs were tested for influenza viruses and 457 for SARS-CoV-2. Only three swabs (0.6%) were positive for Influenza, while SARS-CoV-2 was found in 30 swabs (6.6%). We showed that no circulation of SARS-CoV-2 was detectable in BIS during the 2019/2020 influenza season, while virtually no influenza viruses were found in BIS 2020/2021 during the COVID-19 pandemic.

Is influenza B/Yamagata extinct and what public health implications could this have? An updated literature review and comprehensive assessment of global surveillance databases

“…Ten studies reported data for the Northern hemisphere 2019-2020 influenza season: in only two of these there were B/Yamagata detections, which represented a very minor percentage of all influenza-positive specimens (1 out of 1,683 in Panatto et al, Italy [ Panatto 2021 ], and 6 out of 28,176 in Hu et al, USA [ Hu 2021 ]). In two more studies (Heinzinger et al, Germany, and Ríos-Silva et al, Mexico), data collection started in 2019 and ended in 2021 or, respectively, 2022 [ Heinzinger 2021, Rios-Silva 2021 ]: in both studies, there were no B/Yamagata detections after the 2019-2020 season.…”

“…Of the remaining 587 articles, 547 were discarded for not matching the inclusion criteria (of these, 62 were not further considered since no reported influenza cases were type B), 7 for being based on the WHO FluNet and/or GISAID database, 3 for being previous reports from the GIHSN, and 4 because of overlap with more recent and/or larger articles based on the same data sources. A total of 26 articles were included in the systematic review: their main characteristics are reported in Table 1 [ Soldevila 2022, Murillo-Zamora 2021, Korsun 2021, Panatto 2021, Pablo-Marcos 2020, Miron 2021, Hu 2021, Omer 2022, Olson 2022, Auvinen 2022, Kuzmanovska 2021, Wagatsuma 2022, Heinzinger 2021, Rios-Silva 2022, Suntronwong 2021, da Costa 2022, Melidou 2020, Huang 2022, O’Neill 2022, Kolosova 2022, Peck 2023, Chon 2023, Merced-Morales 2022, Melidou 2022, Sominina 2022, Song 2022 ]. Europe was the most represented area (12 articles, of which 2 reported findings from multiple countries in the WHO European Region), followed by Asia (n=6), North America (n=5), and Oceania and South America (n=1 each).…”

Scenario modelling for diminished influenza seasons during 2020/2021 and 2021/2022 in England

“…We did not incorporate temporally varying contact patterns to capture school holidays, or the possibility of social mixing patterns changing around dates tied to special occasions (the Christmas and New Year period, for example). Finally, given the relative novelty of the SARS- CoV-2 virus in humans, there remains a great amount of uncertainty in our understanding of the interaction of SARS-CoV-2 with other respiratory infections in circulation, such as influenza [32]. We did not consider the consequences of interaction between SARS-CoV-2 and seasonal influenza, such as coinfections.…”

The German Influenza Gap 2021 - A Multifactorial View

“…In the same period of 2019 of the 2019/20 flu season, 165 036 cases were reported. The ECDC also notes in Flu News for the 2020/2021 season that the positive rate of sentinel samples has fallen to 0.1% [8].…”