Influenza virus activity in the world
31 August 2012
Based on FluNet reporting (as of 28 August 2012, 12:00 UTC), during weeks 32 to 33 (5 to 18 August 2012), National Influenza Centres (NICs) and other national influenza laboratories from 68 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 10 575 specimens. 2 127 were positive for influenza viruses, of which 1 620 (76.2%) were typed as influenza A and 507 (23.8%) as influenza B. Of the sub-typed influenza A viruses, 97 (6.7%) were influenza A(H1N1)pdm09 and 1 348 (93.3%) were influenza A(H3N2). Of the characterized B viruses, 141 (75.8%) belong to the B-Yamagata lineage and 45 (24.2%) to the B-Victoria lineage.
During weeks 32 and 33, influenza activity decreased in the southern hemisphere with fewer laboratory confirmed influenza positives being reported. Globally, A(H3N2) viruses remained the predominant subtype followed by influenza B and A(H1N1)pdm09 viruses.
In the Oceania region, a further decrease in influenza activity was reported from Australia and New Zealand. New Caledonia continued to report local outbreaks of A(H3N2) viruses. Influenza A(H3N2) viruses remained the predominant virus in the region.
Varying levels of influenza virus activity were reported from the African region. Increased detections of influenza B viruses were reported from South Africa, while sporadic influenza activity of A(H3N2), A(H1N1)pdm09 and B viruses was reported from Central and East Africa.
In Central and South America, influenza activity remained low with sporadic detections of A(H1N1)pdm09 and influenza B viruses, except in Chile, where influenza A(H3N2) activity remained high.
In Asia, A(H3N2) influenza activity remained high in south mainland China. Elsewhere in the region, sporadic detections of A(H1N1)pdm09, A(H3N2) and influenza B viruses were reported.
Influenza activity remained low in Europe and North America.
In the United States of America, an increase in the number of cases with A(H3N2)v viruses was reported bringing the total to 276 as of 23 August 2012.