Influenza virus activity in the world
1 February 2013
Based on FluNet reporting (as of 29 January 2013, 11:30 UTC), during weeks 2 to 3 (6 to 19 January 2013), National Influenza Centres (NICs) and other national influenza laboratories from 96 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 79 656 specimens. 21 782 were positive for influenza viruses, of which 17 939 (82.4%) were typed as influenza A and 3 843 (17.6%) as influenza B. Of the sub-typed influenza A viruses, 3 489 (32.1%) were influenza A(H1N1)pdm09 and 7 371 (67.9%) were influenza A(H3N2). Of the characterized B viruses, 204 (89.9%) belong to the B-Yamagata lineage and 23 (10.1%) to the B-Victoria lineage.
During weeks 2 to 3, influenza activity continued to increase in parts of the northern hempishere, while in the southern hemisphere influenza activity remained sporadic. A(H3N2) viruses predominated, followed by influenza B and A(H1N1)pdm09 viruses.
Influenza activity increased in Europe with a variable proportion of influenza viruses circulating throughout the region. Increased detections of A(H1N1)pdm09 viruses were reported from the central and eastern European region. A predominance of influenza B viruses were reported from a few countries, while in some other countries A(H3N2) viruses predominated.
Influenza activity remained high in North America, although laboratory confirmed detections declined. Influenza A(H3N2) continued to be the predominant circulating viruses. Influenza B viruses remained predominant in Mexico. The first case of oseltamivir resistant A(H1N1)pdm09 virus for the 2012-2013 season was reported from the United States of America.
High influenza A(H3N2) activity was reported from some countries in Asia, notably China and Japan. Influenza A(H1N1)pdm09 and A(H3N2) activity continued to be reported from some other countries in central and southeast Asia..
In Africa, influenza B viruses co-circulated with A(H1N1)pdm09 viruses. Increased detections of A(H1N1)pdm09 were reported from Algeria. A number of countries in southern, central and west Africa have reported sporadic detections of A(H3N2) and influenza B viruses.
Influenza activity remained sporadic in central and south America with the exception of the Plurinational State of Bolivia, where a number of A(H3N2) detections were reported.