Influenza virus activity in the world

29 July 2011

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

Virological summary

During weeks 27 to 28 (3 to 16 July 2011), influenza activity continued to increase in parts of the southern hemisphere. In Australia and New Zealand typical seasonal activity was observed with a greater number of laboratory confirmed cases detected than in previous weeks. Variable levels of activity were reported, with co-circulation of influenza A(H1N1)2009 and B.

In the southern and central African region, co-circulation of influenza A(H1N1)2009, A(H3N2) and B virus was reported in countries as Cameroon, Ghana and Kenya. A decrease in detection has been observed in South Africa in the past two weeks, with slightly more influenza A(H1N1)2009 than influenza B reported.

Overall influenza activity in South America has been low, but increased influenza A(H1N1)2009 was detected in Chile. In Central America, the Dominican Republic and Honduras reported co-circulation of influenza A(H1N1)2009, A(H3N2) and B.

In the northern hemisphere, influenza activity remain very low and sporadic, concurring with out-of-season levels.

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 27 to 28 (3 to 16 July 2011), National Influenza Centres (NICs) from 35 countries, areas or territories reported data to FluNet*. A total of 945 specimens were reported as positive for influenza viruses, 664 (70.3%) were typed as influenza A and 281 (29.7%) as influenza B. Of the sub-typed influenza A viruses reported, 48.7% were influenza A(H1N1)2009 and 49.5% were influenza A(H3N2).

(FluNet data as of 28 July 2011 12:18 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, Bangladesh, Brazil, Cambodia, Cameroon, Chile, China, Ghana, Honduras, India, Kenya, Madagascar, New Zealand, Oman, Singapore, South Africa, Sri Lanka and Viet Nam
  • Influenza A(H3N2): Australia, Bangladesh, Brazil, Chile, China, Ghana, Honduras, India, Madagascar, Mexico, New Zealand, Republic of Korea, Rwanda, Singapore and South Africa
  • Influenza A(H5): no report
  • Influenza B: Australia, Bangladesh, Cambodia, Cameroon, Chile, China, El Salvador, Ghana, Honduras, India, Iran (Islamic Republic of), Kenya, Madagascar, Mauritius, Mexico, New Zealand, Republic of Korea, Singapore, South Africa, Sri Lanka, United States of America, Viet Nam and Zambia
  • No influenza detected: Algeria, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bulgaria, Central African Republic, France, Georgia, Guatemala, Indonesia, Japan, Kazakhstan, Lao People's Democratic Republic, Lithuania, Nepal, Netherlands, Poland, Romania, Russian Federation, Senegal, Slovakia, Slovenia, Sweden and United Kingdom