Seasonal influenza during the COVID-19 pandemic in Bangladesh

Zubair Akhtar; Fahmida Chowdhury; Mahmudur Rahman; Probir Kumar Ghosh; Md Kaousar Ahmmed; Md Ariful Islam; Joshua A Mott; William Davis

doi:10.1371/journal.pone.0255646

Seasonal influenza during the COVID-19 pandemic in Bangladesh

PLoS One. 2021 Aug 3;16(8):e0255646. doi: 10.1371/journal.pone.0255646. eCollection 2021.

Authors

Zubair Akhtar¹, Fahmida Chowdhury¹, Mahmudur Rahman¹, Probir Kumar Ghosh¹, Md Kaousar Ahmmed¹, Md Ariful Islam¹, Joshua A Mott², William Davis²

Affiliations

¹ International Center for Diarrheal Diseases, Bangladesh, (icddr,b) Programme for Emerging Infections, Dhaka, Bangladesh.
² Influenza Division, Centers for Disease Control and Prevention Regional Influenza Program, Bangkok, Thailand.

Abstract

Introduction: During the 2019 novel coronavirus infectious disease (COVID-19) pandemic in 2020, limited data from several countries suggested reduced seasonal influenza viruses' circulation. This was due to community mitigation measures implemented to control the pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We used sentinel surveillance data to identify changes in the 2020 influenza season compared with previous seasons in Bangladesh.

Methods: We used hospital-based influenza surveillance (HBIS) data of Bangladesh that are generated year-round and are population-representative severe acute respiratory infection (SARI) data for all age groups from seven public and two private tertiary care level hospitals data from 2016 to 2019. We applied the moving epidemic method (MEM) by using R language (v4.0.3), and MEM web applications (v2.14) on influenza-positive rates of SARI cases collected weekly to estimate an average seasonal influenza curve and establish epidemic thresholds.

Results: The 2016-2019 average season started on epi week 18 (95% CI: 15-25) and lasted 12.5 weeks (95% CI: 12-14 weeks) until week 30.5. The 2020 influenza season started on epi week 36 and ended at epi week 41, lasting for only five weeks. Therefore, influenza epidemic started 18 weeks later, was 7.5 weeks shorter, and was less intense than the average epidemic of the four previous years. The 2020 influenza season started on the same week when COVID-19 control measures were halted, and 13 weeks after the measures were relaxed.

Conclusion: Our findings suggest that seasonal influenza circulation in Bangladesh was delayed and less intense in 2020 than in previous years. Community mitigation measures may have contributed to this reduction of seasonal influenza transmission. These findings contribute to a limited but growing body of evidence that influenza seasons were altered globally in 2020.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Bangladesh / epidemiology
COVID-19 / epidemiology
COVID-19 / pathology*
COVID-19 / virology
Databases, Factual
Humans
Influenza, Human / epidemiology*
Pandemics
SARS-CoV-2 / isolation & purification
Seasons
Tertiary Care Centers

Grants and funding

This hospital-based influenza surveillance was funded by the Influenza Division of Centers for Disease Control and Prevention (CDC), Atlanta, under the co-operative agreement (6 NU51IP000852-05-01). icddr,b is grateful to the Governments of Bangladesh, Canada, Sweden, and the UK for providing core/unrestricted support. The funders had no conflict of interest with the contents of the manuscript.