Influenza virus activity in the world

20 July 2012

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

Based on FluNet reporting (as of 17 July 2012, 11:45 UTC), during weeks 26 to 27 (24 June 2012 to 7 July 2012), National Influenza Centres (NICs) and other national influenza laboratories from 67 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 16 337 specimens. 2 265 were positive for influenza viruses, of which 1 895 (83.7%) were typed as influenza A and 370 (16.3%) as influenza B. Of the sub-typed influenza A viruses, 142 (8.3%) were influenza A(H1N1)pdm09 and 1571 (91.7%) were influenza A(H3N2). Of the characterized B viruses, 45 (83.3%) belong to the B-Yamagata lineage and 9 (16.7%) to the B-Victoria lineage.


During weeks 26 and 27, influenza activity continued to increase in the southern hemisphere with varying levels of activity reported. Globally, influenza A(H3N2) viruses remain the predominant virus followed by influenza B and A(H1N1)pdm09 viruses.

In New Zealand influenza activity increased above the expected baseline level. A(H3N2) remained the predominant circulating virus in Australia and New Zealand.

In the southern and central African region, some countries reported increased co-circulation of Influenza A(H3N2) and B viruses, except Ethiopia where A(H1N1)pdm09 viruses predominated.

In Central and South America, increased activity of influenza B and A(H3N2) viruses was reported in Ecuador, while Chile and Paraguay experienced continued activity of A(H3N2) and influenza A(H1N1)pdm09 respectively. Influenza B viruses were predominant in Cuba, Panama and Peru.

In Asia, previously reported unusual levels of influenza A(H3N2) activity in China Hong Kong Special Administrative Region started declining.

In the northern hemisphere sporadic detection of influenza viruses continued to be reported.

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