Epidemiology of seasonal influenza in the Middle East and North Africa regions, 2010-2016: Circulating influenza A and B viruses and spatial timing of epidemics

Abstract

Background: There is a limited knowledge regarding the epidemiology of influenza in Middle East and North Africa.

Objectives: We described the patterns of influenza circulation and the timing of seasonal epidemics in countries of Middle East and North Africa.

Methods: We used virological surveillance data for 2010-2016 from the WHO FluNet database. In each country, we calculated the median proportion of cases that were caused by each virus type and subtype; determined the timing and amplitude of the primary and secondary peaks; and used linear regression models to test for spatial trends in the timing of epidemics.

Results: We included 70 532 influenza cases from seventeen countries. Influenza A and B accounted for a median 76.5% and 23.5% of cases in a season and were the dominant type in 86.8% and 13.2% of seasons. The proportion of influenza A cases that were subtyped was 85.9%, while only 4.4% of influenza B cases were characterized. For most countries, influenza seasonality was similar to the Northern Hemisphere, with a single large peak between January and March; exceptions were the countries in the Arabian Peninsula and Jordan, all of which showed clear secondary peaks, and some countries had an earlier primary peak (in November-December in Bahrain and Qatar). The direction of the timing of influenza activity was east to west and south to north in 2012-2013 and 2015-2016, and west to east in 2014-2015.

Conclusions: The epidemiology of influenza is generally uniform in countries of Middle East and North Africa, with influenza B playing an important role in the seasonal disease burden.

Keywords: Middle East; North Africa; influenza type A; influenza type B; timing of epidemics.

Figure 1

Countries included in the analysis (in red) and countries that were not included because of lack of data (in grey). Countries were marked using the two‐letter ISO codes. AF, Afghanistan; AM, Armenia; BH, Bahrain; DZ, Algeria; EG, Egypt; GE, Georgia; IL, Israel; IQ, Iraq; IR, Iran; JO, Jordan; LB, Lebanon; MA, Morocco; OM, Oman; PK, Pakistan; QA, Qatar; TN, Tunisia; TR, Turkey

Figure 2

Typical timing of the primary and secondary peaks of influenza detection (as calculated using the periodic annual function; see text for details) by site, against their longitudinal and latitudinal positions