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. 2020 Feb 18;20(1):148.
doi: 10.1186/s12879-020-4827-0.

Burden and seasonality of medically attended influenza like illness (ILI) in Ethiopia, 2012 to 2017

Musse Tadesse  1 , Mesfin Mengesha  2 , Adamu Tayachew  2 , Desalegn Belay  2 , Abdulhafiz Hassen  2 , Abyot Bekele Woyessa  2 , Etsehiwot Zemelak  2 , Berhan Beyene  2 , Wubayehu Kassa  2 , Workenesh Ayele  2 , Bethel Teshome  2 , Mikias Mekonen  2 , Zewdu Assefa  2 , Beyene Moges  2
Affiliations

Burden and seasonality of medically attended influenza like illness (ILI) in Ethiopia, 2012 to 2017

Musse Tadesse et al. BMC Infect Dis. .

Abstract

Background: The influenza virus spreads rapidly around the world in seasonal epidemics, resulting in significant morbidity and mortality. Influenza-related incidence data are limited in many countries in Africa despite established sentinel surveillance. This study aimed to address the information gap by estimating the burden and seasonality of medically attended influenza like illness in Ethiopia.

Method: Influenza sentinel surveillance data collected from 3 influenza like illness (ILI) and 5 Severe Acute Respiratory Illness (SARI) sites from 2012 to 2017 was used for analysis. Descriptive statistics were applied for simple analysis. The proportion of medically attended influenza positive cases and incidence rate of ILI was determined using total admitted patients and catchment area population. Seasonality was estimated based on weekly trend of ILI and predicted threshold was done by applying the "Moving Epidemic Method (MEM)".

Result: A total of 5715 medically attended influenza suspected patients who fulfills ILI and SARI case definition (77% ILI and 23% SARI) was enrolled. Laboratory confirmed influenza virus (influenza positive case) among ILI and SARI suspected case was 25% (1130/4426) and 3% (36/1289). Of which, 65% were influenza type A. The predominantly circulating influenza subtype were seasonal influenza A(H3N2) (n = 455, 60%) and Influenza A(H1N1)pdm09 (n = 293, 38.81%). The estimated mean annual influenza positive case proportion and ILI incidence rate was 160.04 and 52.48 per 100,000 population. The Incidence rate of ILI was higher in the age group of 15-44 years of age ['Incidence rate (R) = 254.6 per 100,000 population', 95% CI; 173.65, 335.55] and 5-14 years of age [R = 49.5, CI 95%; 31.47, 130.43]. The seasonality of influenza has two peak seasons; in a period from October-December and from April-June.

Conclusion: Significant morbidity of influenza like illness was observed with two peak seasons of the year and seasonal influenza A (H3N2) remains the predominantly circulating influenza subtype. Further study need to be considered to identify potential risks and improving the surveillance system to continue early detection and monitoring of circulating influenza virus in the country has paramount importance.

Keywords: Ethiopia; ILI; Incidence rate; Influenza; SARI; Seasonality.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Geographical location of ILI and SARI sentinel surveillance sites in Ethiopia
Fig. 2
Fig. 2
Schematic plan of analysis
Fig. 3
Fig. 3
Medically attended influenza positive case (ILI) proportion and incidence rate per 100, 000 population from 2012 to 2017, Ethiopia
Fig. 4
Fig. 4
Medically attended influenza positive case among the total admission (a) and incidence rate (b) of ILI per 100, 000 population by age group, 2012–2017, Ethiopia
Fig. 5
Fig. 5
Trend of medically attended Influenza positive cases by year from 2012 to 2017, Ethiopia
Fig. 6
Fig. 6
Monthly distribution of medically attended influenza virus-positive cases by subtype among Seasonal influenza patients in eight sentinel sites of Ethiopia, 2012–2017
Fig. 7
Fig. 7
Seasonality and threshold (Very high, High and Epidemic) of medically attended influenza (ILI) in the lower administrative level catchment population, 2012–2017 (MEM epidemic curve and average curve)
Fig. 8
Fig. 8
Time series of weekly detection of influenza like illness per year in Ethiopia and seasonal model (MEM application) from 2012 to 2017
See this image and copyright information in PMC

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