Influenza virus activity in the world

12 August 2011

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

Virological summary

During weeks 29 to 30 (17 July 2001 to 30 July 2011) influenza activity continued to increase in some countries in the southern hemisphere.

In Australia, a steady increase of laboratory confirmed cases was observed, with influenza A(H1N1)2009 and B co-circulating in most of the country and influenza B being more predominant in South Australia and also in New Zealand. In South Africa, the influenza season peaked in the previous weeks and the number of laboratory confirmed cases declined, with sporadic activity of influenza A(H1N1)2009. Across South America, low levels of influenza A(H1N1)2009 and A(H3N2) have been reported in Bolivia, Argentina and Brazil. An increase of A(H1N1)2009 was observed in Chile and Uruguay within the expected levels for the season. Low activity and variable detection of influenza A(H1N1)2009, A(H3N2) and B was reported in Central America and the Caribbean, with sporadic detection of influenza B in the Dominican Republic, and influenza A(H3N2) in Cuba.

Throughout the northern hemisphere, the influenza activity remains at very low level.

The vast majority of recently characterized viruses remain antigenically similar to the WHO recommended vaccines for the 2010-2011 northern hemisphere and 2011 southern hemisphere influenza seasons.

During weeks 29 to 30 (17 July 2011 to 30 July 2011), National Influenza Centres (NICs) from 52 countries, areas or territories reported data to FluNet*. A total of 1009 specimens were reported as positive for influenza viruses, 685 (67.9%) were typed as influenza A, 324 (32.1%) as influenza B. Of the sub-typed influenza A viruses reported, 51.8% were influenza A(H1N1)2009 and 48% were influenza A(H3N2).

(FluNet data as of 9 August 2011 12:50 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)2009: Argentina, Australia, Cambodia, Cameroon, Chile, China, Costa Rica, Dominican Republic, Ghana, India, Kenya, Madagascar, New Zealand, Rwanda, South Africa, Thailand, Togo, Viet Nam
  • Influenza A(H3N2): Argentina, Australia, Bangladesh, Brazil, Canada, Chile, China, Ghana, India, Iran (Islamic Republic of), Japan, Lao People's Democratic Republic, Madagascar, Mauritius, New Zealand, South Africa, Thailand, Togo, United States of America
  • Influenza A(H5): Cambodia
  • Influenza B: Argentina, Australia, Bangladesh, Brazil, Cambodia, Cameroon, China, Ghana, India, Japan, Kenya, Madagascar, Mexico, Mauritius, New Zealand, Republic of Korea, South Africa, Sweden, Thailand, Togo, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • No influenza detected: Algeria, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Estonia, Finland, France, Georgia, Germany, Ireland, Latvia, Lithuania, Netherlands, Paraguay, Poland, Romania, Russian Federation, Senegal, Slovakia, Slovenia, Spain