Influenza update

06 April 2015 - Update number 234, based on data up to 22 March 2015


Globally, influenza activity decreased further but remained above the seasonal threshold in the northern hemisphere. While influenza A(H3N2) viruses predominated this season, the proportions of influenza B and influenza A(H1N1)pdm09 detections increased in the last few weeks.

  • In North America, influenza activity continued to decrease but remained slightly above the threshold while the proportion influenza B detections increased.
  • In Europe, influenza activity continued to decline in most countries. Influenza A(H3N2)virus continued to predominate this season, but there was an increase in the proportion of influenza B detections in many countries.
  • In northern Africa and the Middle East, influenza activity decreased in most of the region. Influenza A(H1N1)pdm09 remained predominant in the region.
  • In western Asia, influenza activity decreased in most countries in the region. But influenza detections have increased in Turkey with influenza B and influenza A(H1N1)pdm09 co-circulating.
  • In the temperate countries of Asia, influenza activity continued to decrease in most of the region, but increased in the Republic of Korea. In north China, influenza B activity increased, while the peak of influenza activity occurred in the beginning of the year.
  • In tropical countries of the Americas, influenza activity was reported to decrease in most countries. (corrected on 9 April 2015 from earlier version of published report)
  • In tropical Asia, influenza activity remained high and influenza A(H1N1)pdm09 predominated in India and Bhutan. Influenza activity with influenza A(H3N2) and B continued to decrease from its peak in southern China and China Hong Kong Special Administrative Region.
  • In the southern hemisphere, influenza activity remained at inter-seasonal levels.
  • Based on FluNet reporting (as of 2 April 2015 14:15 UTC), National Influenza Centres (NICs) and other national influenza laboratories from 88 countries, areas or territories reported data for the time period from 8 March 2015 to 21 March 2015. The WHO GISRS laboratories tested more than 87 715 specimens. 17 828 were positive for influenza viruses, of which 9119 (51.1%) were typed as influenza A and 8707 (48.9%) as influenza B. Of the sub-typed influenza A viruses, 2558 (49.8%) were influenza A(H1N1)pdm09 and 2579 (50.2%) were influenza A(H3N2). Of the characterized B viruses, 427 (97.7%) belonged to the B-Yamagata lineage and 10 (2.3%) to the B-Victoria lineage.

Full 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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