Influenza

Influenza update

23 March 2015 - Update number 233, based on data up to 8 March 2015

Summary

Globally, influenza activity remained elevated in the northern hemisphere with influenza A(H3N2) viruses predominating, although some countries in Asia, Europe and North Africa reported high levels of activity associated with influenza A(H1N1)pdm09 viruses.

  • In North America, influenza activity was decreasing but remained above the threshold. Influenza A(H3N2) viruses predominated so far this season.
  • In Europe, influenza activity appeared to have peaked in many countries. Influenza A(H3N2)virus continued to be predominant.
  • In northern Africa and the middle East, influenza activity continued to decrease with influenza A(H1N1)pdm09 viruses predominating, except in Egypt, where there was co-circulation with influenza A(H3N2) and influenza B viruses.
  • In the temperate countries of eastern Asia, influenza A(H3N2) was predominant Asia with very little influenza A(H1N1)pdm09 virus activity, while in western Asia, influenza A(H1N1)pdm09 and influenza B were predominant.
  • In tropical countries of the Americas, influenza activity remained low with mainly A(H3N2) viruses detected.
  • In tropical Asia, influenza activity patterns varied with influenza(H1N1)pdm09 predominant in Bhutan and India, influenza A(H3N2) predominant in the Hong Kong Special Administrative Region, and influenza B predominant in south China.
  • In the southern hemisphere, influenza activity continued at inter-seasonal levels.
  • The term “swine flu” has recently been used incorrectly to refer to the seasonal influenza A(H1N1)pdm09 virus which infects humans during influenza season. The term “swine flu” means influenza viruses that circulate in swine population (pigs) and infect pigs. A(H1N1)pdm09 is not “swine flu” virus. Please see the link below for more information on the terminology of influenza viruses infections in humans.
  • Based on FluNet reporting (as of 19 March 2015 13:25 UTC), National Influenza Centres (NICs) and other national influenza laboratories from 95 countries, areas or territories reported data for the time period from 22 February 2015 to 7 March 2015. The WHO GISRS laboratories tested more than 111 964 specimens. 27 176 were positive for influenza viruses, of which 17 711 (65.2%) were typed as influenza A and 9464 (34.8%) as influenza B. Of the sub-typed influenza A viruses, 3383 (33.9%) were influenza A(H1N1)pdm09 and 6594 (66.1%) were influenza A(H3N2). Of the characterized B viruses, 1903 (97.1%) belonged to the B-Yamagata lineage and 57 (2.9%) 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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