Influenza virus activity in the world

7 December 2012

Source: Laboratory confirmed data from the Global Influenza Surveillance and Response System (GISRS).

Based on FluNet reporting (as of 4 December 2012, 11:45 UTC), National Influenza Centres (NICs) and other national influenza laboratories from 84 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 36067 specimens. 2877 were positive for influenza viruses, of which 2014 (70.0%) were typed as influenza A and 863 (30.0%) as influenza B. Of the sub-typed influenza A viruses, 207 (17.8%) were influenza A(H1N1)pdm09 and 952 (82.1%) were influenza A(H3N2). Of the characterized B viruses, 19 (57.6%) belong to the B-Yamagata lineage and 14 (42.4%) to the B-Victoria lineage.


During weeks 46 and 47, influenza activity increased in the northern hemisphere while remaining sporadic in the southern hemisphere. Globally, A(H3N2) viruses remains the predominant circulating subtype followed by influenza B and A(H1N1)pdm09 viruses.

Influenza activity continued to increase throughout the United States of America most notably in the southern region with A(H3N2) viruses predominant. In Canada, influenza A(H3N2) activity increased slightly. In contrast, activity in Europe has remained low with sporadic detections of A(H1N1)pdm09, A(H3N2) and influenza B viruses reported.

In Central and South America, influenza activity has remained low. Influenza B viruses continue to co-circulate with A(H3N2) and A(H1N1)pdm09 viruses. In Honduras, a higher circulation of A(H3N2) viruses was reported while A(H1N1)pdm09 viruses continued to circulate in Cuba and Peru.

In Asia, regional A(H3N2) activity was reported in Cambodia, with an increase in influenza B detections during week 47. Increased A(H3N2) activity was also reported from Sri Lanka. In general in the region, influenza B viruses predominated.

In Africa, influenza viruses continued to circulate in east and west Africa at lower levels while increasing in Algeria, in the north.

A new case of A(H3N2)v was detected in Iowa, USA, bringing the total number of cases detected in 2012 to 307 .

Other analyses