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WHO Guidelines for Pharmacological Management of Pandemic Influenza A(H1N1) 2009 and Other Influenza Viruses. Geneva: World Health Organization; 2010 Feb.

Cover of WHO Guidelines for Pharmacological Management of Pandemic Influenza A(H1N1) 2009 and Other Influenza Viruses

WHO Guidelines for Pharmacological Management of Pandemic Influenza A(H1N1) 2009 and Other Influenza Viruses.

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4Epidemiology

Currently, WHO publishes weekly information from global influenza surveillance5. As of December 2009, the most prevalent circulating influenza virus was pandemic (H1N1) 2009. The following figure shows the breakdown of results of laboratory testing of 7380 influenza viral isolates from 27 countries (mostly in the Northern Hemisphere):

Characterization of circulating influenza viruses Dec 2009.

Figure

Characterization of circulating influenza viruses Dec 2009.

For the purpose of development of these revised guidelines, it is anticipated that the prevalent influenza viruses in the coming year are most likely to be pandemic (H1N1) 2009, H3N2 and influenza B virus strains, as is reflected in the vaccine composition recommendations for the Southern Hemisphere 2010 season.6

The impact of pandemic (H1N1) 2009 virus infection has been highest in the paediatric and younger adult populations, when measured by attack rates and hospitalization rates.

Influenza A (H5N1) virus (avian influenza) continues to cause sporadic human infections in some countries, with 72 cases (32 deaths) reported in 2009 in 5 countries.7 Thus, although pandemic influenza A (H1N1) 2009 virus may displace other circulating influenza A virus strains, novel influenza A viruses, such as H5N1, remain a pandemic threat.

Footnotes

5

Situation updates - Pandemic (H1N1) 2009. World Health Organization. Available at: http://www​.who.int/csr​/disease/swineflu/updates/en/index​.html. Last accessed on 10 February 2010.

6

Pandemic influenza a (H1N1) 2009 virus vaccine – conclusions and recommendations from the October 2009 meeting of the immunization Strategic Advisory Group of Experts. World Health Organization, Weekly Epidemiological Record, 4 December 2009, 8449:505-509. Available at: http://www​.who.int/wer/2009/wer8449.pdf. Last accessed on 10 February 2010. [PubMed: 19960623]

Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO. World Health Organization, 30 December 2009. Available at: http://www​.who.int/csr​/disease/avian_influenza​/country/cases_table_2009_12_30​/en/index.html. Last accessed on 10 February 2010.

Copyright © 2010, World Health Organization.
Bookshelf ID: NBK138516

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