Influenza virus activity in the world
7 January 2013
Based on FluNet reporting (as of 3 January 2013, 12:40 UTC), during weeks 50 to 51 (9 December 2012 to 22 December 2012), National Influenza Centres (NICs) and other national influenza laboratories from 77 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 36 007 specimens. 5 528 were positive for influenza viruses, of which 4 013 (72.6%) were typed as influenza A and 1 515 (27.4%) as influenza B. Of the sub-typed influenza A viruses, 431 (17.2%) were influenza A(H1N1)pdm09 and 2 078 (82.8%) were influenza A(H3N2). Of the characterized B viruses, 52 (69.3%) belong to the B-Yamagata lineage and 23 (30.7%) to the B-Victoria lineage.
During weeks 50 and 51 influenza activity continued to increase in the northern hemisphere while sporadic activity was reported from the southern hemisphere. Influenza A(H3N2) viruses remained the predominant subtype globally, followed by influenza B and A(H1N1)pdm09 viruses.
In North America, influenza activity increased and varied from localized to widespread in both Canada and the United States of America with influenza A(H3N2) as the predominant subtype. In contrast, influenza B viruses were the predominant subtype in Mexico.
In Europe, influenza activity continued to increase across the region. In recent weeks, increased activity was reported from Denmark and France. Influenza A(H1N1)pdm09, A(H3N2) and B viruses co-circulated in the region.
Increased A(H3N2) activity was reported from China and Japan while sporadic activity was reported from the region.
In the Eastern Mediterranean region, increased A(H1N1)pdm09 virus detections were reported from the West Bank and Gaza Strip where 9 deaths were recorded. Increased A(H1N1)pdm09 activity was reported from elsewhere in the region as well as A(H3N2) and influenza B viruses.
In Africa, increased detections of influenza B viruses were reported from Algeria while A(H1N1)pdm09 viruses were detected in the Democratic Republic of the Congo.
In the northern hemisphere, 426 A(H3N2), 49 A(H1N1)pdm09, and 164 B viruses have been tested for antiviral resistance to neuraminidase inhibitors and all have remained sensitive to oseltamivir and zanamivir.