Influenza

Influenza virus activity in the world

4 November 2011

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

Virological summary

During weeks 41 to 42 (9 October 2011 to 22 October 2011), laboratory confirmed influenza virus detection remained low in most parts of the world with only a few countries in Africa, Asia and central America reporting local or regional outbreaks. The majority of viruses circulating globally were influenza A(H1N1)pdm09 and A(H3N2).

In the northern hemisphere overall influenza activity remained low. In North America and Europe, sporadic detections of influenza A(H1N1)pdm09, A(H3N2) and B viruses continued. In Asia, regional activity of influenza A(H1N1)pdm09 and B viruses continued since week 29 in Cambodia, and in Nepal increased activity of A(H1N1)pdm09 and A(H3N2) was detected.

In central America, Nicaragua reported an increase in influenza activity due to co-circulation of A(H1N1)pdm09 and A(H3N2) viruses.

In the southern hemisphere, influenza A(H1N1)pdm09, A(H3N2) and B viruses continued to circulate at low levels in Africa, Oceania and South America. Local outbreaks of A(H1N1)pdm09 and B continued to be reported in Cameroon.

2 cases of swine origin influenza A(H3N2) infection were reported from the United States of America. Preliminary analysis showed that the 2 viruses are swine origin triple reassortant with the M gene from A(H1N1)pdm09. These are the 6th and 7th cases of viruses with this gene constitution. All previous cases were detected in the United States of America. Further characterization of the viruses is on-going in the WHO Collaborating Centre at the Centers for Disease Control and Prevention (CDC) in Atlanta. Meanwhile, for pandemic preparedness purposes, the WHO GISRS has developed and made available 2 candidate vaccine viruses developed from a swine-origin triple reassortant influenza virus.

FluNet summary

During weeks 41 to 42 (9 October 2011 to 22 October 2011), National Influenza Centres (NICs) from 86 countries, areas or territories reported data to FluNet. A total of 1448 specimens were reported as positive for influenza viruses, 1026 (70.9%) were typed as influenza A and 422 (29.1%) as influenza B. Of the sub-typed influenza A viruses reported, 53.5% were influenza A(H1N1)pdm09 and 46.5% were influenza A(H3N2).

FluNet data as of 3 November 2011 10:40 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)pdm09: Australia, Bolivia (Plurinational State of), Brazil, Cambodia, Cameroon, China, Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, France, France - New Caledonia, Ghana, Honduras, India, Jamaica, Japan, Kenya, Nepal, New Zealand, Nicaragua, Panama, Spain, Sweden, United Kingdom of Great Britain and Northern Ireland, Viet Nam
  • Influenza A(H1N1) old seasonal virus: no report
  • Influenza A(H3N2): Australia, Bolivia (Plurinational State of), Brazil, Burkina Faso, Cambodia, Cameroon, Canada, China, Colombia, Costa Rica, Cuba, Egypt, El Salvador, France, Honduras, India, Japan, Kenya, Lao People's Democratic Republic, Mexico, Nepal, New Zealand, Nicaragua, Norway, Republic of Korea, South Africa, Togo, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • Influenza B: Australia, Bolivia (Plurinational State of), Burkina Faso, Cambodia, Cameroon, China, Dominican Republic, Germany, Guatemala, Honduras, India, Iran (Islamic Republic of), Japan, Kenya, Lao People's Democratic Republic, Madagascar, Netherlands, New Zealand, Norway, Poland, South Africa, Togo, United Kingdom of Great Britain and Northern Ireland, United States of America, Viet Nam
  • No influenza detected: Albania, Algeria, Angola, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria, Central African Republic, Croatia, Denmark, Estonia, Ethiopia, Fiji, Finland, Georgia, Greece, Hungary, Iceland, Indonesia, Ireland, Kyrgyzstan, Latvia, Lithuania, Luxembourg, Malta, Mauritius, Portugal, Republic of Moldova, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Switzerland, Tunisia, Turkey, Ukraine, Zambia
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Snapshot global influenza virus circulation (GISRS-FluNet, 3 November 2011)