Influenza virus activity in the world

22 June 2012

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

Based on FluNet reporting (as of 19 June 2012, 14:30 UTC), during weeks 22 to 23 (27 May 2012 to 9 June 2012), National Influenza Centres (NICs) and other national influenza laboratories from 79 countries, areas or territories reported data. The WHO GISRS laboratories tested more than 16 552 specimens. 1 959 were positive for influenza viruses, of which 1 489 (76%) were typed as influenza A and 421 (21.5%) as influenza B. Of the sub-typed influenza A viruses, 146 (11%) were influenza A(H1N1)pdm09 and 1 176 (88.8%) were influenza A(H3N2). Of the characterized B viruses, 10 (50%) belong to the B-Yamagata lineage and 10 (50%) to the B-Victoria lineage.


During weeks 22 and 23 in 2012, laboratory confirmed influenza activity remained low in many parts of the northern hemisphere. In the southern hemisphere the influenza season started in some countries with local outbreaks reported. Globally, A(H3N2) viruses remained the dominant virus followed by influenza B and influenza A(H1N1)pdm09 viruses respectively.

In Asia, influenza A(H3N2) activity has remained high in the China Hong Kong Special Administrative Region. In week 23, a detection of an oseltamivir resistant influenza A(H1N1)pdm09 virus, the 20th case since 2009, was reported.

In Europe, influenza activity was low with sporadic detections reported.

In North America, among the continuing declining detections of influenza viruses, influenza B viruses outnumbered A(H3N2) viruses in recent weeks.

In Central America an increase of influenza activity has been observed. A regional outbreak of influenza A(H1N1)pdm09 viruses was reported in El Salvador.

In Africa, local outbreaks of predominantly A(H3N2) viruses were reported in Madagascar while influenza A(H1N1)pdm09 virus activity increased in Rwanda. Influenza B viruses remain the predominant virus in South Africa. Overall influenza A(H3N2) remains the predominant virus in the African region.

Sporadic activity of influenza A(H3N2) and B viruses has been detected in Oceania.

In South America, influenza A(H1N1)pdm09, A(H3N2) and B viruses have been co-circulating in the temperate and tropical countries. A local outbreak of A(H3N2) was reported in Chile and detections of influenza A(H1N1)pdm09 and A(H3N2) viruses increased in Brazil.

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