Influenza update

18 May 2015 - Update number 237, based on data up to 2 May 2015


Globally, influenza activity has been low. In the northern hemisphere influenza activity was nearing inter-seasonal levels and in the southern hemisphere influenza activity remained low. Countries in the tropical zones reported low influenza activity with the exception of some countries in tropical Asia and west Africa.

  • In North America, influenza activity continued to decrease and was near inter-seasonal levels. Continued but decreasing influenza B circulation resulted in a slow decline of the influenza season.
  • In Europe, influenza activity mainly associated with influenza B virus continued to decline in most countries.
  • In northern Africa, influenza activity decreased to almost inter-seasonal levels with mainly influenza B detections in the last weeks.
  • In western Asia, influenza activity decreased further, with predominantly influenza A(H1N1)pdm09 detections in recent weeks, especially in Jordan.
  • In the temperate countries of Asia, there was little to no activity throughout the region with only a few influenza B detections in the past weeks.
  • In tropical countries of the Americas, influenza activity remained low in most countries, with the exception of Guatemala which showed a slight increase in influenza A(H3N2) detections.
  • In tropical Asia, influenza activity was low and in general continued to decrease in most countries. In west Africa, several countries reported increased influenza detections.
  • In the southern hemisphere, influenza activity remained at low or inter-seasonal levels.
  • Based on FluNet reporting (as of 12 May 2015 14:05 UTC), National Influenza Centres (NICs) and other national influenza laboratories from 86 countries, areas or territories reported data for the time period from 19 April 2015 to 2 May 2015. The WHO GISRS laboratories tested more than 51 009 specimens. 4728 were positive for influenza viruses, of which 1234 (26.1%) were typed as influenza A and 3494 (73.9%) as influenza B. Of the sub-typed influenza A viruses, 456 (53.8%) were influenza A(H1N1)pdm09 and 391 (46.2%) were influenza A(H3N2). Of the characterized B viruses, 285 (94.7%) belonged to the B-Yamagata lineage and 16 (5.3%) to the B-Victoria lineage.

Detailed influenza update

Influenza surveillance outputs

Seasonal update

For regional updates on influenza see the following links

For updates on the influenza at the human-animal interface see the following WHO web pages:

Source of data

The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.
The updates are based on available epidemiological and virological data sources, including FluNet (reported by the WHO Global Influenza Surveillance and Response System) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.


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