Influenza virus activity in the world
12 October 2012
Based on FluNet reporting (as of 9 October 2012, 14:35 UTC), during weeks 38 to 39 (16/09/2012 to 29/09/2012), National Influenza Centres (NICs) and other national influenza laboratories from 88 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 12 712 specimens. 823 were positive for influenza viruses, of which 457 (55.5%) were typed as influenza A and 366 (44.5%) as influenza B. Of the sub-typed influenza A viruses, 95 (24.7%) were influenza A(H1N1)pdm09 and 289 (75.3%) were influenza A(H3N2). Of the characterized B viruses, 6 (31.6%) belong to the B-Yamagata lineage and 13 (68.4%) to the B-Victoria lineage.
During weeks 38 to 39, influenza activity remained low throughout most parts of the world. Influenza A(H3N2) viruses remained the predominant circulating virus subtype globally, followed by influenza B and A(H1N1)pdm viruses.
In Central and South America, influenza B was the predominant circulating virus in the region. Sporadic detections of influenza A(H1N1)pdm09 and A(H3N2) viruses were reported but in lower numbers compared to previous weeks.
Influenza activity continued to decrease in the Oceania region. Influenza A(H3N2) and influenza B viruses co-circulated in Australia and New Zealand.
In Africa, increased influenza A(H3N2) activity has been reported from Cameroon and Central African Republic while Senegal reported increased detections of A(H1N1)pdm09 viruses. Influenza viruses have been reported sporadically from elsewhere in the region.
Sporadic influenza detections were reported from most countries in Asia. Cambodia continued to report regional influenza A(H3N2) and influenza B virus activity while influenza detections of A(H1N1)pdm09 and B viruses decreased in Nepal.
Sporadic detections of influenza A(H3N2) and influenza B viruses have been reported from Europe. Seasonal influenza activity continued to remain low in North America.