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2009 H1N1 Flu: International Situation Update

Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

January 4, 2010, 5:00 PM ET

This report provides an update to the international situation as of January 4, 2010. The World Health Organization (WHO) continues to report laboratory-confirmed 2009 H1N1 flu cases and deathsExternal Web Site IconExternal Web Site Icon on its Web page. These laboratory-confirmed cases represent a substantial underestimation of total cases in the world, as most countries focus surveillance and laboratory testing only on people with severe illness. The 2009 H1N1 influenza virus continues to be the dominant influenza virus in circulation in the world. For the most recent period in which data are available, from December 13 to December 19, 2009, 87% of influenza specimens reported to WHO were 2009 H1N1, 0.2% were seasonal A (H1), 1.6% were A (H3), 7.7% were influenza A viruses that were not subtyped, and 3.4% were influenza B viruses. In temperate regions of the Southern Hemisphere, sporadic cases of 2009 H1N1 continue to be reported but no sustained community transmission has been observed. In tropical regions of the Americas and Asia, influenza activity due to 2009 H1N1 remains variable. In temperate regions of the Northern Hemisphere, influenza-like illness (ILI) activity due to 2009 H1N1 has returned to baseline or below baseline in North America. Overall, pandemic influenza activity appears to have peaked in most Western European countries but remains active in Central and Eastern European countries. In Western and Central Asia, influenza activity continues to persist above baseline levels.

Selected Highlights

  • The 2009 H1N1 influenza virus is the predominant influenza virus in circulation worldwide.
  • According to WHO, the majority of 2009 H1N1 influenza isolates tested worldwide remain sensitive to oseltamivir, an antiviral medicine used to treat influenza disease. 168 2009 H1N1 isolates tested worldwide have been found to be resistant to oseltamivir – 50 of these isolates were detected in the United States.
  • On September 17, 2009, several countries including the United States announced plans to donate 2009 H1N1 vaccine or funds to support vaccination campaigns in less developed countries.

International Resources for 2009 H1N1 Information

Health Organizations

World Health Organization (WHO) Regional Offices

Travel and 2009 H1N1 Flu

Human cases of 2009 H1N1 flu virus infection have been identified in the United States and several countries around the world. For information on 2009 H1N1 flu and travel, see the CDC H1N1 Flu and Travel website.

Reports and Publications

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