Influenza virus activity in the world
6 July 2012
Based on FluNet reporting (as of 4 July 2012, 07:00 UTC), during weeks 24 to 25 (10 June 2010 to 23 June 2012), National Influenza Centres (NICs) and other national influenza laboratories from 70 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 12 952 specimens. 1 559 were positive for influenza viruses, of which 1 285 (82.4%) were typed as influenza A and 274 (17.6%) as influenza B. Of the sub-typed influenza A viruses, 176 (15.4%) were influenza A(H1N1)pdm09 and 967 (84.6%) were influenza A(H3N2). Of the characterized B viruses, 27 (93.1%) belong to the B-Yamagata lineage and 2 (6.9%) to the B-Victoria lineage.
During weeks 24 and 25 in 2012, laboratory confirmed influenza activity continued increasing in the southern hemisphere with A(H3N2) viruses predominant. In the northern hemisphere activity remained low in general.
In the southern hemisphere, increased influenza activity has been reported in Australia and New Zealand with A(H3N2) as the predominant circulating subtype.
In Africa, influenza activity increased steadily. Ghana and South Africa were experiencing increased co-circulation of A(H3N2) and influenza B viruses while Madagascar continued to report local outbreaks of A(H3N2). Influenza A(H1N1)pdm09 virus continued to circulate in Rwanda at a lower level.
In central and South America, circulation of influenza A and B viruses were detected. Increased activity of influenza A(H1N1)pdm09 viruses and associated outbreaks were reported in Bolivia (Plurinational State of), El Salvador and Paraguay, while in Brazil and Chile increased activity of A(H3N2) and associated outbreaks were detected. In Ecuador influenza B predominated.
In the northern hemisphere, sporadic detections of influenza A(H1N1)pdm09, A(H3N2) and B viruses continued to be reported in low levels, except in Hong Kong, SAR China, where unusually high level of A(H3N2) activity continued.