Influenza

Influenza virus activity in the world

21 April 2011

Source: Laboratory confirmed data from the Global Influenza Surveillance Network (GISN).

Virological summary

During weeks 13 to 14, a number of countries reported a significantly lower number of laboratory confirmed detections of influenza A(H1N1)2009, A(H3N2) and B viruses than in previous weeks.

In the northern hemisphere, influenza activity due to A(H1N1)2009 and B viruses continued to decrease in Asia, most countries in Europe and North America. Relatively few countries reported A(H3N2) activity.

In the southern hemisphere and most tropical regions, influenza activity due to A(H1N1)2009, A(H3N2) and B viruses remained low. The Dominican Republic and Venezuela however reported an increase in A(H1N1)2009 activity. An outbreak of A(H1N1)2009 was also reported in Mexico where the viruses were shown to be closely related to the WHO recommended A(H1N1)2009 vaccine virus.

The vast majority of characterized viruses from the 2010-2011 influenza season remain antigenically similar to the viruses WHO recommended for the 2010-2011 northern hemisphere influenza vaccines.

During weeks 13 to 14 (27 March 2011 to 09 April 2011), National Influenza Centres (NICs) from 69 countries, areas or territories reported data to FluNet*. A total of 4 170 specimens were reported as positive for influenza viruses, 2 123 (50.9%) were typed as influenza A, 2 047 (49.1%) as influenza B. Of the sub-typed influenza A viruses reported, 59.8% were influenza A(H1N1)2009 and 40.1% were influenza A(H3N2).

(FluNet data as of 19 April 2011 12:40 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: Algeria, Armenia, Australia, Austria, Belarus, Bulgaria, Cambodia, Cameroon, Canada, China, Croatia, Denmark, Dominican Republic, Estonia, Democratic Republic of the Congo, France, Georgia, Germany, Ghana, Hungary, Iceland, India, Iran (Islamic Republic of), Israel, Italy, Kenya, Lao People's Democratic Republic, Latvia, Mauritius, Mexico, Mongolia, Netherlands, Norway, Poland, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Sri Lanka, Sweden, Switzerland, Tunisia, Turkey, Ukraine, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • Influenza A(H1N1) (old seasonal virus): Mauritius
  • Influenza A(H3N2): Australia, Austria, Brazil, Canada, China, Cuba, Denmark, Democratic Republic of the Congo, France, Italy, Japan, Kenya, Latvia, Madagascar, Norway, Republic of Korea, Russian Federation, Rwanda, Sweden, Turkey, United States of America
  • Influenza A(H5): Cambodia
  • Influenza B: Australia, Austria, Belarus, Belgium, Bulgaria, Cambodia, Canada, China, Croatia, Denmark, Dominican Republic, Estonia, Ethiopia, Finland, France, Georgia, Germany, Ghana, Hungary, Iceland, Iran (Islamic Republic of), Israel, Italy, Japan, Kenya, Lao People's Democratic Republic, Latvia, Lithuania, Luxembourg, Madagascar, Mexico, Netherlands, Norway, Poland, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Sri Lanka, Sweden, Switzerland, Tunisia, Turkey, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • No influenza activity reported: Afghanistan, Azerbaijan, Bosnia and Herzegovina, Central African Republic, Colombia, Costa Rica, Ecuador, El Salvador, Honduras, Jamaica, Kyrgyzstan, Mali, Malta, Morocco, Paraguay, Portugal
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Snaphot global influenza virus circulation (GISN-FluNet, 19 April 2011)