# Epidemiological patterns of influenza viruses among severe acute respiratory infection patients in Burkina Faso, 2016-2019: a surveillance study

## TL;DR

This study found that influenza viruses, especially type A, were common among hospitalized severe respiratory infection patients in Burkina Faso, with children under five most affected.

## Contribution

The study provides new epidemiological data on influenza virus prevalence and subtype distribution among severe respiratory infection patients in Sub-Saharan Africa.

## Key findings

- Influenza virus was detected in 20.1% of severe acute respiratory infection patients.
- Influenza A was the most common type, with A(H1N1)pmd09 being the predominant subtype.
- Children aged 1-4 years were most affected, with a high proportion of influenza A infections.

## Abstract

influenza viruses cause acute respiratory infections; however, their importance among severe cases remains poorly documented in Sub-Saharan Africa. This study aimed to describe the burden of influenza among inpatients admitted for severe acute respiratory infections (SARI) in Burkina Faso.

a surveillance study was conducted between 2016 and 2019 by the National Influenza Reference Laboratory (NIRL). Inpatients admitted for SARI from four sentinel surveillance sites were included and tested for influenza using a real-time reverse transcription-polymerase chain reaction (rRT-PCR) with the Fast Track Diagnostics (FTD-33) Kits. Positive samples to influenza virus type A or B were further subtyped using the CDC Primers, probes, and protocols. Descriptive analysis was used to assess the prevalence of influenza according to participants' medical and sociodemographic characteristics using the R statistical package. A p-value less than 0.05 was considered statistically significant.

overall, the prevalence of influenza was 20.1% (310/1541). Influenza virus type-specific prevalence was 13.0% (200/1,541), 6.1% (94/1,541), and 1.0% (16/1,541) for type A, B, and C viruses, respectively. Among the cases, type A virus was predominant with 64.4% (52.4% for A(H1N1)pmd09 and 12.0% for A(H3N2)) and type B virus with 30.4% (21.7% for B/Victoria and 8.1% for B/Yamagata). Three waves of increased transmission were observed during the study period, and each was dominated by a specific virus subtype. The distribution of cases according to sociodemographic characteristics showed that children aged 1-4 years were mostly affected (60%), mainly with type A virus (36.9%), followed by infants below 1 year of age (21%), also with type A virus (15.2%). Virus circulation occurred year-round, and transmission peaks occurred during the cold and dry seasons.

type A influenza virus was predominant, especially among children under five years old. Prioritizing vaccination among preschool-aged children, particularly during the seasonal peaks, might yield the most public health impact.