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.

Background: Adults with cardiopulmonary conditions are at increased risk for complications from influenza and respiratory syncytial virus (RSV) infection, but few data are available from middle-income countries. Methods: Using data from a prospective cohort study of influenza vaccine effectiveness among community-dwelling Thai adults aged ≥65 years, we estimated and compared the incidence of influenza and RSV in those with and without cardiopulmonary conditions. During May 2015-May 2017, older adults in a rural province in Thailand were followed weekly with year-round surveillance for acute respiratory illness (ARI), defined broadly as new onset or worsening of cough with or without fever, and hospitalized ARI. When ill, nasal self-swabs and/or nasopharyngeal swabs were collected for reverse-transcription polymerase chain reaction testing. We used Poisson regression to calculate incidence rate ratios (IRR), adjusting for age, sex, past healthcare-seeking behavior, weekly influenza activity, and influenza vaccination. Results: Overall, 3,220 adults with a median age of 71 years (IQR 68-76) were enrolled; 1,324 (41.1%) were male; and 313 (9.7%) had ≥1 underlying cardio-pulmonary condition, most commonly chronic obstructive pulmonary disease (131; 41.2%) or asthma (73; 23.3%). Compared to those without, participants with cardiopulmonary conditions had higher incidences of ARI, influenza, and RSV (Adjusted IRR: 1.83, 95% CI 1.63-2.05; 1.84, 95% CI 1.05-3.23; 2.02, 95% CI 1.10-3.72, respectively). Conclusion: Our findings show that older adults in rural Thailand with cardiopulmonary conditions have increased rates of ARI, influenza, and RSV infections, and support efforts to ensure this population has access to influenza vaccines and other respiratory illness prevention measures.