Based on FluNet reporting (as of 18 June 2013, 09:10 UTC), during weeks 22 to 23 (26 May 2013 to 8 June 2013), National Influenza Centres (NICs) and other national influenza laboratories from 66 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 14 646 specimens. 906 were positive for influenza viruses, of which 615 (67.9%) were typed as influenza A and 291 (32.1%) as influenza B. Of the sub-typed influenza A viruses, 354 (74.4%) were influenza A(H1N1)pdm09 and 122 (25.6%) were influenza A(H3N2). Of the characterized B viruses, 10 (71.4%) belong to the B-Yamagata lineage and 4 (28.6%) to the B-Victoria lineage.

Summary

During weeks 22 and 23, influenza activity remained low globally. Influenza A(H1N1)pdm09 viruses continued to be the predominant circulating subtype, followed by influenza B and A(H3N2) viruses.

In Asia and Oceania, influenza A(H3N2) and influenza B viruses co-circulated throughout the region at low levels in general, although Viet Nam reported increased A(H1N1)pdm09 virus activity.

In Africa, A(H1N1)pdm09 activity remained high in Madagascar and South Africa. Sporadic influenza detections were reported from elsewhere in the region.

In Central and South America, A(H1N1)pdm09 viruses continued to circulate although at low levels.

In Europe and North America sporadic detections of influenza B viruses continued to be reported