Influenza virus activity in the world

9 September 2011

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

Virological summary

During weeks 33 to 34 (14 August 2011 to 27 August 2011), the number of influenza viruses detected by laboratories continued to decrease in most parts of the southern hemisphere, while in the northern hemisphere the activity remained low.

In Australia the influenza activity remained at low levels, with slight increases in some regions of co-circulation of influenza A(H1N1)2009 and B viruses. In New South Wales in Australia, a cluster of 25 cases of influenza A(H1N1)2009 has been detected of oseltamivir resistance associated with an H275Y substitution in NA.

In Africa, in the temperate region, sporadic detections of A(H1N1)2009 and B were reported in some countries, while in some parts of the southern region, influenza A(H1N1)2009 and A(H3N2) were detected at very low levels.

In South America, influenza A(H3N2) activity in general declined, except in Cuba a slight increase was observed. Some countries in South America reported no influenza virus detections.

In the United States of America, 4 cases of swine origin influenza (SOI) A(H3N2) have been reported in children in Indiana and Pennsylvania. The viruses from these 4 cases are swine origin triple reassortant A(H3N2), but have the M gene from human A(H1N1)2009 virus. These viruses are antigenically similar to each other, and similar to previous SOI viruses isolated from human cases in the US. Further investigation is ongoing.

The vast majority of viruses characterized recently in the WHO Global Influenza Surveillance and Response System (GISRS) remain antigenically similar to the WHO recommended vaccine viruses for the 2010-2011 northern hemisphere and 2011 southern hemisphere influenza seasons.

During weeks 33 to 34 (14 August 2011 to 27 August 2011), National Influenza Centres (NICs) from 68 countries, areas or territories reported data to FluNet*. A total of 1008 specimens were reported as positive for influenza viruses, 736 (73%) were typed as influenza A and 272 (27%) as influenza B. Of the sub-typed influenza A viruses reported, 50.2% were influenza A(H1N1)2009 and 49.7% were influenza A(H3N2).

(FluNet data as of 6 September 2011 14:30 UTC)

* Some NICs report to FluNet retrospectively leading to updates of previous summary data.

Influenza virus detection by type/subtype in countries, areas or territories:

  • Influenza A(H1N1)2009: Argentina, Australia, Bolivia (Plurinational State of), Brazil, Cambodia, Cameroon, Chile, China, Colombia, France - French Guiana, Ghana, Honduras, India, Japan, Kenya, Madagascar, New Zealand, Singapore, Slovakia, South Africa, Togo, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • Influenza A(H1N1) old seasonal virus: no report
  • Influenza A(H3N2): Argentina, Australia, Brazil, Chile, China, Costa Rica, Cuba, El Salvador, Ghana, Honduras, India, Lao People's Democratic Republic, Madagascar, Mexico, New Zealand, Peru, Rwanda, Senegal, Singapore, South Africa, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • Influenza A(H5): no report
  • Influenza B: Australia, Brazil, Cambodia, Cameroon, Chile, China, Dominican Republic, Ghana, Honduras, India, Kenya, Lao People's Democratic Republic, Mauritius, New Zealand, Norway, Republic of Korea, Singapore, Slovakia, South Africa, Sri Lanka, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam, Zambia
  • No influenza detected: Algeria, Angola, Armenia, Austria, Azerbaijan, Belarus, Bosnia and Herzegovina, Bulgaria, Denmark, Dominican Republic, Estonia, Finland, France, France - Guadeloupe, France - Martinique, Georgia, Germany, Iceland, Indonesia, Iran (Islamic Republic of), Ireland, Latvia, Lithuania, Netherlands, Panama, Paraguay, Poland, Republic of Moldova, Romania, Russian Federation, Slovenia, Spain, Sweden, Ukraine