Influenza virus activity in the world
13 May 2013
Based on FluNet reporting (as of 7 May 2013, 10:30 UTC), during weeks 16 to 17 (14 to 27 April 2013), National Influenza Centres (NICs) and other national influenza laboratories from 80 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 41 698 specimens. 4384 were positive for influenza viruses, of which 2400 (54.7%) were typed as influenza A and 1984 (45.3%) as influenza B. Of the sub-typed influenza A viruses, 1224 (67.3%) were influenza A(H1N1)pdm09, 595 (32.7%) were influenza A(H3N2). Of the characterized B viruses, 91 (85%) belonged to the B-Yamagata lineage and 16 (15%) to the B-Victoria lineage.
During weeks 16 and 17, A(H1N1)pdm09 viruses were predominant globally followed by A(H3N2) and influenza B viruses. Influenza activity remained low in the northern and southern hemisphere.
In Europe and North America, laboratory confirmed detections of influenza B viruses decreased compared to previous weeks. Overall, influenza activity remained low.
In Asia influenza activity was low. In the eastern parts of Asia, A(H3N2) and A(H1N1)pdm09 viruses were detected, while in the southern parts in general, co-circulation of A(H1N1)pdm09 and influenza B viruses were reported.
Influenza A(H1N1)pdm09 and influenza B viruses co-circulated at low levels in the African region.
Sporadic influenza activity of all three circulating subtypes was reported from Oceania.
Sporadic activity of influenza A(H1N1)pdm09 and A(H3N2) remained in Central and South America.
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