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Influenza transmission during COVID-19 measures downscaling in Greece, August 2022: evidence for the need of continuous integrated surveillance of respiratory viruses.

ABSTRACT: After the near absence of influenza and other respiratory viruses during the first 2 years of the COVID-19 pandemic, an increased activity of mainly influenza A(H3N2) was detected at the beginning of August 2022 in Greece on three islands. Of 33 cases with respiratory symptoms testing negative for SARS-CoV-2 with rapid antigen tests, 24 were positive for influenza: 20 as A(H3N2) subtype and four as A(H1N1)pdm09 subtype. Phylogenetic analysis of selected samples from both subtypes was performed and they fell into clusters within subclades that included the 2022/23 vaccine strains. Our data suggest that influenza can be transmitted even in the presence of another highly infectious pathogen, such as SARS-CoV-2, with a similar transmission mode. We highlight the need for implementing changes in the current influenza surveillance and suggest a move from seasonal to continuous surveillance, especially in areas with a high number of tourists. Year-round surveillance would allow for a timelier start of vaccination campaigns and antiviral drugs procurement processes.

SUBMITTER: Mellou K

PROVIDER: S-EPMC10347892 | biostudies-literature | 2023 Jul

REPOSITORIES: biostudies-literature

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Influenza transmission during COVID-19 measures downscaling in Greece, August 2022: evidence for the need of continuous integrated surveillance of respiratory viruses.

Mellou Kassiani K Tryfinopoulou Kyriaki K Emmanouil Mary M Gkolfinopoulou Kassiani K Sapounas Spyros S Evangelidou Maria M Moulopoulou Panagiota P Miaoulis Eleftherios E Angelakis Emmanouil E Sourvinos George G Zaoutis Theoklis T Paraskevis Dimitrios D

Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin 20230701 28

After the near absence of influenza and other respiratory viruses during the first 2 years of the COVID-19 pandemic, an increased activity of mainly influenza A(H3N2) was detected at the beginning of August 2022 in Greece on three islands. Of 33 cases with respiratory symptoms testing negative for SARS-CoV-2 with rapid antigen tests, 24 were positive for influenza: 20 as A(H3N2) subtype and four as A(H1N1)pdm09 subtype. Phylogenetic analysis of selected samples from both subtypes was performed a ...[more]

PMID: 37440348

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Project description:ImportanceInfluenza virus infections declined globally during the COVID-19 pandemic. Loss of natural immunity from lower rates of influenza infection and documented antigenic changes in circulating viruses may have resulted in increased susceptibility to influenza virus infection during the 2021-2022 influenza season.ObjectiveTo compare the risk of influenza virus infection among household contacts of patients with influenza during the 2021-2022 influenza season with risk of influenza virus infection among household contacts during influenza seasons before the COVID-19 pandemic in the US.Design, setting, and participantsThis prospective study of influenza transmission enrolled households in 2 states before the COVID-19 pandemic (2017-2020) and in 4 US states during the 2021-2022 influenza season. Primary cases were individuals with the earliest laboratory-confirmed influenza A(H3N2) virus infection in a household. Household contacts were people living with the primary cases who self-collected nasal swabs daily for influenza molecular testing and completed symptom diaries daily for 5 to 10 days after enrollment.ExposuresHousehold contacts living with a primary case.Main outcomes and measuresRelative risk of laboratory-confirmed influenza A(H3N2) virus infection in household contacts during the 2021-2022 season compared with prepandemic seasons. Risk estimates were adjusted for age, vaccination status, frequency of interaction with the primary case, and household density. Subgroup analyses by age, vaccination status, and frequency of interaction with the primary case were also conducted.ResultsDuring the prepandemic seasons, 152 primary cases (median age, 13 years; 3.9% Black; 52.0% female) and 353 household contacts (median age, 33 years; 2.8% Black; 54.1% female) were included and during the 2021-2022 influenza season, 84 primary cases (median age, 10 years; 13.1% Black; 52.4% female) and 186 household contacts (median age, 28.5 years; 14.0% Black; 63.4% female) were included in the analysis. During the prepandemic influenza seasons, 20.1% (71/353) of household contacts were infected with influenza A(H3N2) viruses compared with 50.0% (93/186) of household contacts in 2021-2022. The adjusted relative risk of A(H3N2) virus infection in 2021-2022 was 2.31 (95% CI, 1.86-2.86) compared with prepandemic seasons.Conclusions and relevanceAmong cohorts in 5 US states, there was a significantly increased risk of household transmission of influenza A(H3N2) in 2021-2022 compared with prepandemic seasons. Additional research is needed to understand reasons for this association.

Dataset Information

Influenza transmission during COVID-19 measures downscaling in Greece, August 2022: evidence for the need of continuous integrated surveillance of respiratory viruses.

Publications

Influenza transmission during COVID-19 measures downscaling in Greece, August 2022: evidence for the need of continuous integrated surveillance of respiratory viruses.

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