Influenza virus activity in the world

23 September 2011

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

Virological summary

During weeks 35 to 36 (28 August 2011 to 10 September 2011), the number of laboratory confirmed influenza viruses reported remained low in most parts of the world. In the southern hemisphere, however, regional outbreaks continued to be reported in Australia and New Zealand.

The predominant circulating influenza virus types/subtypes differed in various countries.

Influenza A(H1N1)2009, A(H3N2) and B viruses co-circulated in Australia while the predominant viruses in New Zealand were A(H3N2) and B. In Africa, A(H1N1)2009 and B circulated in Cameroon with sporadic detections of A(H1N1)2009, A(H3N2) and B virus reported in some other countries. In South America, influenza viruses circulated at low levels with the exception of Cuba and Peru where localized activity of A(H3N2) was reported.

In the northern hemisphere influenza activity in general was very low, except Cambodia where regional outbreaks of A(H1N1)2009 and B continued to be reported.

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 the 2011 southern hemisphere influenza season. A WHO consultation will take place from 26 to 29 September 2011 to review the data generated and collected by the WHO GISRS together with other available information and to recommend composition of influenza vaccines for the southern hemisphere 2012.

During weeks 35 to 36 (28 August 2011 to 10 September 2011), National Influenza Centres (NICs) from 69 countries, areas or territories reported data to FluNet*. A total of 1023 specimens were reported as positive for influenza viruses, 745 (72.8%) were typed as influenza A and 278 (27.2%) as influenza B. Of the sub-typed influenza A viruses reported, 43.3% were influenza A(H1N1)2009 and 56.7% were influenza A(H3N2).

(FluNet data as of 20 September 2011 09:00 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: Australia, Bolivia (Plurinational State of), Brazil, Cambodia, Cameroon, Chile, China, Dominican Republic, France - New Caledonia, Ghana, Honduras, India, New Zealand, Panama, South Africa, United States of America, Viet Nam
  • Influenza A(H1N1) old seasonal virus: no report
  • Influenza A(H3N2): Australia, Bolivia (Plurinational State of), Brazil, Burkina Faso, Cambodia, Chile, China, Cuba, Egypt, Ghana, Guatemala, Honduras, India, Kenya, Lao People's Democratic Republic, Madagascar, Mauritius, Mexico, Netherlands, New Zealand, Republic of Korea, South Africa, Thailand, Togo, United States of America
  • Influenza A(H5): no report
  • Influenza B: Australia, Burkina Faso, Cambodia, Cameroon, Chile, China, Democratic Republic of the Congo, Ghana, Honduras, India, Iran (Islamic Republic of), Kenya, Mauritius, New Zealand, Poland, South Africa, Sri Lanka, Thailand, Viet Nam
  • No influenza detected: Afghanistan, Algeria, Angola, Armenia, Austria, Azerbaijan, Belarus, Bosnia and Herzegovina, Bulgaria, Central African Republic, Colombia, Costa Rica, Estonia, Ethiopia, Finland, France, Georgia, Germany, Iceland, Ireland, Jamaica, Japan, Lithuania, Malaysia, Norway, Paraguay, Republic of Moldova, Romania, Russian Federation, Rwanda, Slovakia, Slovenia, Sweden

WHO Consultation on the Composition of Influenza Vaccine for the Southern Hemisphere 2012

Snapshot global influenza virus circulation (GISRS-FluNet, 20 September 2011)