Influenza virus activity in the world
14 October 2013
Based on FluNet reporting (as of 8 October 2013, 11:30 UTC), during weeks 38 to 39 (15 September 2013 to 28 September 2013), National Influenza Centres (NICs) and other national influenza laboratories from 81 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 17 704 specimens. 1277 were positive for influenza viruses, of which 996 (78%) were typed as influenza A and 281 (22%) as influenza B. Of the sub-typed influenza A viruses, 248 (31.1%) were influenza A(H1N1)pdm09 and 549 (68.9%) were influenza A(H3N2). Of the characterized B viruses, 23 (69.7%) belong to the B-Yamagata lineage and 10 (30.3%) to the B-Victoria lineage.
During weeks 38 and 39, A(H3N2) viruses were the predominant subtype detected globally followed by A(H1N1)pdm09 and influenza B viruses. In general, influenza activity was low in the northern hemisphere and moderate to sporadic in the southern hemisphere.
Influenza A(H3N2) and B viruses co-circulated in the African region. Increased detections of A(H3N2) were reported from the Central African Republic and Ghana while sporadic activity was reported from elsewhere.
In the Oceania region, A(H1N1)pdm09 and A(H3N2) viruses continued to co-circulate in Australia and New Zealand.
A(H3N2) viruses were predominant in the Asian region with increased detections reported from China.
All circulating influenza viruses were detected at low levels in the Caribbean, Central and South America with the exception of Costa Rica where increased detections of A(H1N1)pdm09 and A(H3N2) viruses were reported compared to previous weeks.
Influenza activity remained low in the North American and European regions.