Influenza virus activity in the world
21 December 2012
Based on FluNet reporting (as of 18 December 2012, 13:05 UTC), during weeks 48 to 49 (25 November 2012 to 8 December 2012), National Influenza Centres (NICs) and other national influenza laboratories from 87 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 40 499 specimens. 5 329 were positive for influenza viruses, of which 3 864 (72.5%) were typed as influenza A and 1465 (27.5%) as influenza B. Of the sub-typed influenza A viruses, 245 (10.5%) were influenza A(H1N1)pdm09 and 2 091 (89.5%) were influenza A(H3N2). Of the characterized B viruses, 38 (50%) belong to the B-Yamagata lineage and 38 (50%) to the B-Victoria lineage.
During weeks 48 and 49, influenza activity increased in the northern hemisphere while remaining sporadic in the southern hemisphere. Globally, influenza A(H3N2) remains the predominant circulating subtype followed by influenza B and A(H1N1)pdm09.
Influenza A(H3N2) activity continued to increase throughout the United States of America. An increase in influenza A(H3N2) activity was also reported in Canada. In Europe activity increased notably in the United Kingdom of Great Britain and Northern Ireland and in Norway, while it remained sporadic in the rest of region.
In Central and South America, influenza activity has remained low with sporadic detections of influenza A(H1N1)pdm09, A(H3N2) and B viruses.
In Asia, influenza A(H3N2) activity increased in China and remained sporadic in the rest of region.
In Africa, influenza activity remained low. Sporadic detections of influenza A(H1N1)pdm09, A(H3N2) and B viruses were reported.
A new case of A(H3N2)v infection was reported in Minnesota, United States of America, bringing the total number of cases detected in 2012 to 308.