Influenza

Influenza update

22 April - Update number 209

Summary

Globally, the northern hemisphere influenza season appeared to be approaching interseasonal levels in most countries. As influenza detections declined, the proportion of influenza B detections increased slightly in many regions, especially Asia, the Middle East, and North America.

  • In North America, influenza levels continued to decline. Late season circulation of influenza B continued; however, the overall numbers of influenza detections remained low.
  • In Europe, influenza activity continued to decrease, as the region appeared to be coming to an end of the influenza season. A rise in the percentage of influenza specimens testing positive was observed, but the overall number of specimens declined. Influenza A(H3N2) and A(H1N1)pdm09 co-circulated, with low numbers of influenza B virus detected. In eastern Europe, influenza activity was higher later in the season compared to the north and the south-west, but detections have begun to decline as well.
  • In Eastern Asia, influenza activity approached interseasonal levels, and influenza B comprised the majority of influenza detections.
  • In Tropical Asia, influenza activity continued to decline.
  • In Northern Africa and Western Asia, influenza activity remained low in most countries, with influenza B the predominant virus detected.
  • In the Southern Hemisphere, influenza activity remained low and detections were sporadic.
  • Based on FluNet reporting (as of 15 April 2014, 10:15 UTC), during weeks 13 to 14 (23 March 2014 to 5 April 2014), National Influenza Centres (NICs) and other national influenza laboratories from 82 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 44 319 specimens. 6717 were positive for influenza viruses, of which 4163 (62%) were typed as influenza A and 2554 (38%) as influenza B. Of the sub-typed influenza A viruses, 1149 (47.2%) were influenza A(H1N1)pdm09 and 1287 (52.8%) were influenza A(H3N2). Of the characterized B viruses, 224 (83%) belong to the B-Yamagata lineage and 46 (17%) to the B-Victoria lineage.

Full influenza update


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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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