Influenza virus activity in the world
27 April 2012
Based on FluNet reporting (as of 24 April 2012, 12:40 UTC), during weeks 14 to 15 (01 April 2012 to 14 April 2012), National Influenza Centres (NICs) and other national influenza laboratories from 78 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 28664 specimens. 6096 were positive for influenza viruses, of which 4477 (73.4%) were typed as influenza A and 1619 (26.6%) as influenza B. Of the sub-typed influenza A viruses, 569 (18.6%) were influenza A(H1N1)pdm09 and 2481 (81.3%) were influenza A(H3N2). Of the characterized B viruses, 197 (69.4%) belong to the B-Yamagata lineage and 87 (30.6%) to the B-Victoria lineage.
During weeks 14 and 15 in 2012, laboratory confirmed influenza activity continued to decrease in the northern hemisphere. Influenza A(H3N2) remained the predominant virus subtype detected globally. Influenza A(H1N1)pdm09 virus activity was low in general with the exception of India where regional outbreaks of this virus subtype were reported. Influenza B virus continued to be the main virus detected in Canada and the Republic of Korea. Globally the proportion of influenza B viruses belonging to the B-Yamagata lineage compared to the B-Victoria lineage viruses have steadily increased over the past few weeks.
In Europe, the number of virus detections declined. Influenza A(H3N2) continued to predominate with co-circulation of influenza B virus in some countries and sporadic detections of A(H1N1)pdm09 viruses.
In North America , influenza A(H3N2) and influenza B remained the predominant virus subtype in the United States of America and Canada respectively. In Central America, A(H1N1)pdm09 was the main circulating virus subtype in several countries while influenza A(H3N2) virus detections increased in the Dominican Republic.
In Asia, influenza A(H3N2) and B viruses co-circulated in China, Japan and a number of other countries.
In the Middle East, Qatar continued to report A(H1N1)pdm09 as the predominant virus subtype but at low levels.
In the southern hemisphere, influenza activity continued to be low with the majority of the sporadic virus detections identified as influenza A(H3N2).