The National Burden of Influenza-Associated Respiratory Illness Among Children Aged <5 Years in Niger, 2015-2018

Influenza contributes substantially to severe acute respiratory infection (SARI) morbidity and mortality worldwide. However, few countries have estimated influenza disease burden, especially middle and low-income countries. Burden data are important to understand the impacts of illness on the population and to inform interventions. Currently, Niger has no recommendations for seasonal influenza vaccination or antiviral use. We estimated the national number and rates of SARI and influenza-associated SARI hospitalizations, mild/moderate illness, and death among children aged < 5 years in Niger.

We utilized influenza surveillance data among children aged < 5 years hospitalized with SARI at three sentinel hospitals located in Niamey during 2015-2018 along with estimated catchment area population data to calculate the influenza-associated SARI hospitalization rates per 100,000 population. Rates were calculated for age groups < 1, 1-4, and < 5 years using the World Health Organization (WHO) methods and a hospital admission survey; then, we extrapolated the estimates nationally. We also used the influenza burden pyramid tool developed by WHO and the John Hopkins Center for Health Security to estimate influenza-associated mild/moderate illnesses and influenza-associated deaths for Niger.

Influenza viruses were detected in 175/1796 (9.7%) specimens collected and tested during the study period from children aged < 5 years at the three SARI sentinel surveillance sites. The influenza percentage positive was 7.7% (58/754) among infants aged < 1 year and 11.3% (117/1038) among children aged 1-4 years. The estimated mean annual national number of SARI hospitalizations among children aged < 5 years was 16,406 (95% CI: 15,117-17,779) and the estimated SARI hospitalization rate per 100,000 population was 405.3 (95% CI: 373.5-439.2). The estimated mean annual national number of influenza-associated SARI hospitalizations among children aged < 5 years was 1484 (95% CI: 1162-1813; rate: 36.7; 95% CI: 28.7-44.8). The estimated mean annual national number of influenza-associated mild illnesses, hospitalized patients, and deaths among children aged < 5 years in Niger was 218,030 (95% CI: 43,303-527,236), 1261 (95% CI: 38-3271), 223 (95% CI: 22-614), and 15 (95% CI: 6-373) respectively.

'This study estimated a substantial influenza disease burden among children aged < 5 years in Niger, highlighting, for decision makers, the importance of resource allocation and public health interventions like vaccination. Future efforts should consider estimating the potential cost-benefit of implementing prevention and control measures (e.g., influenza vaccine or antivirals) among children aged 6-59 months in Niger.