Background: Recent evidences reported that co-infection with SARS-CoV-2 and Influenza virus is common. We explored hospital-based influenza surveillance (HBIS) data during the COVID-19 pandemic. Methods: We analyzed data from March to December 2020 among patients admitted with severe acute respiratory infections (SARI) defined as subjective or measured fever of ≥ 38 C° and cough with onset within the last ten days. Physicians recorded patients’ demographic, clinical, and laboratory information and obtained nasopharyngeal and oropharyngeal swabs to test for influenza virus and SARS-CoV-2 by rRT-PCR. Results: We enrolled 1,986 SARI case-patients with median age of 28 years (IQR: 1.2 ­ 53 years), and 67.6% were male. Among SARI case-patients, 285 (14.3%) were infected with SARS-CoV-2 and 175 (8.8%) infected with influenza virus. Only five (0.3%) SARI patients were co-infected with SARS-CoV-2 and influenza virus. Difficulty breathing (83% vs. 77%, p=0.024) and sore throat (26% vs. 17%, p<0.001) were more likely to be present in SARS-CoV-2-infected SARI patients. SARI case-patients with diabetes and hypertension were more likely (14% vs. 6%, p<0.001 and 27% vs. 12%, p<0.001 respectively) to be infected with SARS-CoV-2 virus than those without co-morbidities. Influenza virus remained undetectable during the first 14 weeks of the 20 weeks (May to September) of peak influenzacirculation period in Bangladesh. Conclusions: Our findings suggest that co-infection with SARS-CoV-2 and influenza virus was not very common together with nonappearance of the influenza virus during most of the peak influenza period in Bangladesh during COVID-19 pandemic. Future studies are warranted for further exploration.

During the 2019 novel coronavirus disease (COVID-19) pandemic in 2020, limited data from several countries suggested reduced circulation of seasonal influenza viruses. We applied the moving epidemic method (MEM) to influenza surveillance data from 2016 to 2019 in Bangladesh to estimate an average seasonal influenza curve and establish epidemic thresholds. The 2020 influenza epidemic started 18 weeks later, was 7.5 weeks shorter, and was less intense than the average curve of the four previous years. These findings contribute to a limited but growing body of evidence that influenza seasons were altered globally in 2020.

Pregnant women with their infants are considered at higher risk for influenza-associated complications, and the WHO recommends influenza vaccination during pregnancy to protect them, including their infants (0-6 months). There are limited data on the influenza burden among pregnant women and their infants (0-6 months), and there is no routine influenza vaccination in Bangladesh. Five annual cohorts (2013-2017) of pregnant women were enrolled from 8 sub-districts of Bangladesh before the influenza season (May-September); contacted weekly to identify new onset of influenza-like illness (ILI) (subjective or measured fever and cough) and acute respiratory illness (ARI) (at least two of: cough, rhinorrhea, or difficulty breathing) among their infants from birth to 6 months of age. We collected nasopharyngeal swabs from ILI and ARI cases, tested by rRT-PCR for influenza virus (including types and subtypes) and estimated influenza incidence (95% CI) /10,000 pregnancy-months or infant-months, respectively. We enrolled 9,020 pregnant women, followed for 26,709 pregnancy-months and detected 1,241 ILI episodes. We also followed 8,963 infants for 51,518 infant-months and identified 5,116 ARI episodes. Influenza positivity was 23% for ILI and 3% for ARI cases. The overall incidence (2013-2017) of influenza among pregnant women was 158.5/10,000 pregnancy-months (95% CI: 141.4-177.6), and that among infants was 21.9/10,000 infant-months (95% CI: 18.2-26.5). Although the data was collected more than five years ago, as the only baseline data, our findings illustrate evidence of influenza burden among pregnant women and infants (0-6 months) which may support preventive policy decisions in Bangladesh.