Influenza virus activity in the world
26 October 2012
Based on FluNet reporting (as of 23 October 2012, 15:00 UTC), ), during weeks 40 to 41 (30/09/2012 to 13/10/2012), National Influenza Centres (NICs) and other national influenza laboratories from 93 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 18 909 specimens. 996 were positive for influenza viruses, of which 575 (57.7%) were typed as influenza A and 421 (42.3%) as influenza B. Of the sub-typed influenza A viruses, 206 (39.4%) were influenza A(H1N1)pdm09 and 317 (60.6%) were influenza A(H3N2). Of the characterized B viruses, 16 (72.7%) belong to the B-Yamagata lineage and 6 (27.3%) to the B-Victoria lineage.
During weeks 40 and 41, influenza activity remained low globally although increased reports of laboratory confirmed influenza positives have been received from some countries in the northern hemisphere. Influenza A(H3N2) viruses remained the predominant subtype globally, followed by influenza B and A(H1N1)pdm09 viruses.
Sporadic detections of influenza viruses have been reported from Europe and North America. In Canada, A(H3N2) and A(H1N1)pdm09 viruses were detected while in the United States of America, influenza B viruses have been predominant followed by A(H3N2) and A(H1N1)pdm09 viruses. In Europe, detections of A(H3N2) and influenza B viruses have been reported.
In Asia, co-circulation of A(H1N1)pdm09 viruses and influenza B viruses continued in India and Nepal. Influenza B viruses remained the predominant subtype in the region. Sporadic detections of influenza A(H1N1)pdm09 and influenza B viruses were reported from Qatar in the Middle East.
In the southern hemisphere, influenza activity has decreased. Influenza activity was reported to be at baseline level in Australia while no reports of laboratory confirmed influenza positives were received from other countries in Oceania.
In Africa, A(H3N2) continued to circulate throughout central, eastern and western Africa.
In Central and South America, influenza activity increased slightly in Argentina, Brazil and Chile compared to previous weeks. Co-circulation of influenza A(H3N2) and B viruses continued in a few countries throughout the region.