Influenza virus activity in the world

7 October 2011

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

Virological summary

During weeks 37 to 38 (11 September 2011 to 24 September 2011), the number of laboratory confirmed influenza viruses reported remained low in most parts of the world. The predominant circulating influenza virus types/subtypes differed in various countries with the majority of detections reported as influenza A.

In the southern hemisphere, slight increased influenza activity due to influenza A(H1N1)pdm09* was reported in Bolivia, while influenza A(H3N2) virus was predominant in several countries in central and South America.

Influenza A(H1N1)pdm09, A(H3N2) and B viruses continued to co-circulate in Australia but in declining levels. Influenza A(H3N2) and B viruses were predominant in New Zealand but were detected at lower levels than in recent weeks. In Africa, sporadic detections of A(H1N1)pdm09, A(H3N2) and B virus were reported in some countries.

In the northern hemisphere influenza activity in general was very low.

Following the WHO consultation which took place from 26 to 29 September 2011 to review the data generated and collected by the WHO GISRS together with other available information, it was recommended that the influenza vaccines for the southern hemisphere 2012 influenza season contain the following viruses:

  • an A/California/7/2009 (H1N1)pdm09-like virus;
  • an A/Perth/16/2009 (H3N2)-like virus;
  • a B/Brisbane/60/2008-like virus.

Availability of candidate vaccine viruses and instructions to obtain these viruses can be found on the WHO influenza vaccine viruses web page.

During weeks 37 to 38 (11 September 2011 to 24 September 2011), National Influenza Centres (NICs) from 73 countries, areas or territories reported data to FluNet. A total of 1299 specimens were reported as positive for influenza viruses, 960 (73.9%) were typed as influenza A and 339 (26.1%) as influenza B. Of the sub-typed influenza A viruses reported, 43.9% were influenza A(H1N1)pdm09 and 56.1% were influenza A(H3N2).

(FluNet data as of 4 October 2011 13:50 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)pdm09: Australia, Bolivia (Plurinational State of), Brazil, Cambodia, Cameroon, Chile, China, Costa Rica, Cuba, Dominican Republic, Ecuador, Ghana, Honduras, India, Kenya, Madagascar, New Zealand, Panama, Singapore, Sri Lanka, Viet Nam
  • Influenza A(H1N1) old seasonal virus: no report
  • Influenza A(H3N2): Argentina, Australia, Bolivia (Plurinational State of), Brazil, Burkina Faso, Cambodia, Cameroon, Chile, China, Costa Rica, Cuba, El Salvador, Guatemala, Honduras, India, Kenya, Lao People's Democratic Republic, Madagascar, New Zealand, Nicaragua, Republic of Korea, Singapore, South Africa, Spain, Sri Lanka, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • Influenza A(H5): no report
  • Influenza B: Australia, Bangladesh, Bolivia (Plurinational State of), Burkina Faso, Cambodia, Cameroon, Chile, China, Ethiopia, India, Kenya, New Zealand, Singapore, South Africa, Spain, Sri Lanka, Uganda, United States of America, Viet Nam
  • No influenza detected: Algeria, Angola, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Central African Republic, Denmark, Egypt, Estonia, Finland, France, Georgia, Germany, Iceland, Iran (Islamic Republic of), Ireland, Jamaica, Japan, Latvia, Lithuania, Malaysia, Mauritius, Netherlands, Norway, Poland, Republic of Moldova, Romania, Russian Federation, Rwanda, Slovakia, Slovenia, Sweden

* previously referred to as A(H1N1)2009