Influenza virus activity in the world
25 November 2013
Based on FluNet reporting (as of 19 November 2013, 12:20 UTC), during weeks 44 to 45 (27 October 2013 to 9 November 2013), National Influenza Centres (NICs) and other national influenza laboratories from 93 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 28 870 specimens. 1318 were positive for influenza viruses, of which 977 (74.1%) were typed as influenza A and 341 (25.9%) as influenza B. Of the sub-typed influenza A viruses, 271 (42%) were influenza A(H1N1)pdm09 and 375 (58%) were influenza A(H3N2). Of the characterized B viruses, 42 (82.4%) belong to the B-Yamagata lineage and 9 (17.6%) to the B-Victoria lineage.
During weeks 44 and 45, influenza activity increased slightly in the northern hemisphere while remaining low in the southern hemisphere. A(H3N2) remained the predominant virus globally, followed by A(H1N1)pdm09 and B viruses.
Sporadic detections of influenza viruses were reported from Australia and New Zealand where influenza activity continued to decrease.
Influenza activity remained low in most of countries in Asia. A(H3N2) activity was reported in China where it remained the predominant virus subtype as well as in Thailand.
All three influenza subtypes circulated throughout Africa at low levels. A(H3N2) and influenza B viruses were detected in Ethiopia and Uganda respectively.
In the European region, sporadic activity was reported from a number of countries with detections of all three subtypes.
In North America, influenza activity increased. In the United States of America, the number of laboratory confirmed detections increased slightly although overall influenza activity was low. In Canada, increased detections of A(H1N1)pdm09 viruses were reported.
Influenza activity decreased in Central and South America where A(H1N1)pdm09 viruses were the predominant virus detected virus at low levels.. Influenza B was reported from some countries in the Caribbean.