Global influenza seasonality to inform country-level vaccine programs: An analysis of WHO FluNet influenza surveillance data between 2011 and 2016

<div><p>By analyzing publicly available surveillance data from 2011–2016, we produced country-specific estimates of seasonal influenza activity for 118 countries in the six World Health Organization regions. Overall, the average country influenza activity period was 4.7 months. Our analysis characterized 100 countries (85%) with one influenza peak season, 13 (11%) with two influenza peak seasons, and five (4%) with year-round influenza activity. Surveillance data were limited for many countries. These data provide national estimates of influenza activity, which may guide planning for influenza vaccination implementation, program timing and duration, and policy development.</p></div

Influenza activity¹ seasonality by World Health Organization region, 2011–2016.

<p>Influenza activity<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193263#t001fn001" target="_blank">¹</a> seasonality by World Health Organization region, 2011–2016.</p

Illustrative examples of influenza seasonality classifications, 2011–2016.

<p>Illustrative examples of influenza seasonality classifications, 2011–2016.</p

Influenza seasonality assessment for Kenya, Malaysia.

<p>Influenza seasonality assessment for Kenya, Malaysia.</p

Data source, definitions and analytic approach to assess influenza seasonality.

<p>Data source, definitions and analytic approach to assess influenza seasonality.</p

Influenza vaccination zones.

<p>Countries with data extrapolated from neighbours are in italics.</p

Primary and secondary influenza activity in the tropics and subtropics.

<p>Primary and secondary influenza activity in the tropics and subtropics.</p

Seasonal influenza vaccination zones.

<p>Seasonal influenza vaccination zones.</p