Influenza

Influenza update

23 February 2015 - Update number 231, based on data up to 7 February 2015

Summary

Globally, influenza activity remained high in the northern hemisphere with influenza A(H3N2) viruses predominating. Some countries reported an increase in influenza A(H1N1)pdm09 activity. Antigenic characterization of most recent A(H3N2) viruses thus far indicated differences from the A(H3N2) virus used in the influenza vaccines for the northern hemisphere 2014-2015. The vast majority of influenza A(H3N2) viruses tested to date this season were sensitive to neuraminidase inhibitors.

  • In North America, the influenza activity seemed to have peaked. Influenza A(H3N2) virus has predominated this season.
  • In Europe, the influenza season continued to rise, particularly in western and central countries. Influenza A(H3N2) remained the dominant virus detected this season. However, in south west Europe the proportion of influenza A(H1N1) and influenza B increased.
  • In northern Africa and the middle East, influenza activity is ongoing. Some countries are reporting an increase in influenza A(H1N1)pdm09 activity (Jordan, Morocco, Tunisia).
  • In the temperate countries of Asia, influenza activity decreased from its peak in northern China, but continued to increase in Mongolia and the Republic of Korea. Influenza A(H3N2) virus predominated so far.
  • In tropical countries of the Americas, influenza activity remained low in most countries.
  • In tropical Asia, influenza activity continued to increase in southern China, China Hong Kong Special Administrative Region and India.
  • In the southern hemisphere, influenza activity remained at inter-seasonal levels.
  • Based on FluNet reporting (as of 20 February 2015 08:25 UTC), during weeks 4 to 5 (25 January 2015 to 7 February 2015), National Influenza Centres (NICs) and other national influenza laboratories from 90 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 138 720 specimens. 32 769 were positive for influenza viruses, of which 26 664 (81.4%) were typed as influenza A and 6105 (18.6%) as influenza B. Of the sub-typed seasonal influenza A viruses, 1580 (12.5%) were influenza A(H1N1)pdm09 and 11 094 (87.5%) were influenza A(H3N2). Of the characterized B viruses, 1813 (97.3%) belonged to the B-Yamagata lineage and 50 (2.7%) to the B-Victoria lineage.

Full influenza update

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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