Influenza virus activity in the world
23 November 2012
Based on FluNet reporting (as of 20 November 2012, 09:40 UTC), during weeks 44 to 45 (28/10/2012 to 10/11/2012), National Influenza Centres (NICs) and other national influenza laboratories from 91 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 34 054 specimens. 1 778 were positive for influenza viruses, of which 1 165 (65.5%) were typed as influenza A and 613 (34.5%) as influenza B. Of the sub-typed influenza A viruses, 222 (26.1%) were influenza A(H1N1)pdm09 and 630 (73.9%) were influenza A(H3N2). Of the characterized B viruses, 20 (55.6%) belong to the B-Yamagata lineage and 16 (44.4%) to the B-Victoria lineage.
During weeks 44 and 45, influenza activity increased slightly in some countries in the northern hemisphere while sporadic influenza detections were reported from the southern hemisphere. Globally, A(H3N2) viruses remains the predominant circulating subtype followed by influenza B and A(H1N1)pdm09 viruses.
In North America, influenza activity increased in some areas. Canada reported increased A(H3N2) activity while the United States of America reported regional influenza activity in 4 states with A(H3N2) viruses co-circulating with influenza B viruses. In Europe, sporadic influenza detections of A(H1N1)pdm09, A(H3N2) and influenza B viruses were reported from the region.
Influenza activity remained low in Asia. A(H3N2) was the predominant circulating subtype followed by A(H1N1)pdm09 and influenza B viruses. A(H3N2) activity remained high in Cambodia however A(H1N1)pdm09 and influenza B viruses have been also been detected in recent weeks.
In Africa, A(H3N2) activity decreased in Cameroon while A(H1N1)pdm09 activity remained high in Ethiopia. In central and south America influenza activity remained low with sporadic detections of influenza viruses being reported. Influenza B continued to co-circulate with A(H3N2) and A(H1N1)pdm09 viruses in some countries.