Types, Subtypes and Positivity Rates of Seasonal Influenza in Uganda, 2019-2023
- 1Uganda Virus Research Institute
Abstract
BackgroundSeasonal influenza, commonly known as flu, is an acute respiratory, highly contagious illness caused by influenza viruses. A clear understanding of influenza seasonality is crucial for guiding prevention and treatment strategies, including decisions on vaccination timing to prevent outbreaks. While well documented in temperate regions, data on influenza epidemiology in tropical areas, particularly sub-Saharan Africa, remain limited. We described the types, subtypes and positivity rate of seasonal influenza in Uganda during 2019-2023.
MethodsThis study used descriptive statistics to understand the characteristics of the data, and then employed multivariable logistic regression to identify factors independently associated with a positive influenza test result. The regression analysis examined the impact of sex, sample type, time of year, and year on influenza positivity, quantifying these associations with odds ratios, confidence intervals, and p-values to assess their statistical significance.
ResultsOf 18035 samples, 938 (5.2%) tested positive for influenza, with a higher prevalence in Influenza-Like Illness (ILI) cases (5.7%) compared to Severe Acute Respiratory Infection (SARI) cases (3.7%). Influenza A was the predominant type (69.7%), followed by influenza B (29.7%, all B. Victoria), with rare co-infections. Among influenza A subtypes, A/H3N2 was most common (65.1%), followed by A/H1N1pdm09 (33.5%). Multivariable logistic regression revealed that the male gender, the month of March, and decreasing year were associated with increased influenza positivity, while SARI sampling and other months showed reduced positivity.
ConclusionThe seasonal influenza positivity rates from 2019 to 2023 and the predominance of Influenza A and H3N2 highlight the need for sustained surveillance in Uganda. Given Influenza As high genetic variability and potential for novel strain emergence, monitoring circulating strains, informing vaccine development, and implementing targeted interventions for high-risk groups and regions are critical to controlling and preventing outbreaks.
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BibTeX
@misc{nankya2026types,
title = {{Types, Subtypes and Positivity Rates of Seasonal Influenza in Uganda, 2019-2023}},
author = {M. A. Nankya and N. Owor and J. T. Kayiwa and J. J. Lutwama and S. Gidudu and G. Bahizi and A. R. Ario},
howpublished = {medRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.29.26361662},
url = {https://www.medrxiv.org/content/10.64898/2026.08.29.26361662v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Types, Subtypes and Positivity Rates of Seasonal Influenza in Uganda, 2019-2023
AU - M. A. Nankya
AU - N. Owor
AU - J. T. Kayiwa
AU - J. J. Lutwama
AU - S. Gidudu
AU - G. Bahizi
AU - A. R. Ario
PY - 2026
DA - 2026/08/29
PB - medRxiv
DO - 10.64898/2026.08.29.26361662
UR - https://www.medrxiv.org/content/10.64898/2026.08.29.26361662v1
AB - BackgroundSeasonal influenza, commonly known as flu, is an acute respiratory, highly contagious illness caused by influenza viruses. A clear understanding of influenza seasonality is crucial for guiding prevention and treatment strategies, including decisions on vaccination timing to prevent outbreaks. While well documented in temperate regions, data on influenza epidemiology in tropical areas, particularly sub-Saharan Africa, remain limited. We described the types, subtypes and positivity rate of seasonal influenza in Uganda during 2019-2023. MethodsThis study used descriptive statistics to understand the characteristics of the data, and then employed multivariable logistic regression to identify factors independently associated with a positive influenza test result. The regression analysis examined the impact of sex, sample type, time of year, and year on influenza positivity, quantifying these associations with odds ratios, confidence intervals, and p-values to assess their statistical significance. ResultsOf 18035 samples, 938 (5.2%) tested positive for influenza, with a higher prevalence in Influenza-Like Illness (ILI) cases (5.7%) compared to Severe Acute Respiratory Infection (SARI) cases (3.7%). Influenza A was the predominant type (69.7%), followed by influenza B (29.7%, all B. Victoria), with rare co-infections. Among influenza A subtypes, A/H3N2 was most common (65.1%), followed by A/H1N1pdm09 (33.5%). Multivariable logistic regression revealed that the male gender, the month of March, and decreasing year were associated with increased influenza positivity, while SARI sampling and other months showed reduced positivity. ConclusionThe seasonal influenza positivity rates from 2019 to 2023 and the predominance of Influenza A and H3N2 highlight the need for sustained surveillance in Uganda. Given Influenza As high genetic variability and potential for novel strain emergence, monitoring circulating strains, informing vaccine development, and implementing targeted interventions for high-risk groups and regions are critical to controlling and preventing outbreaks.
ER -