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Novel H1N1 Flu: International Situation Update

August 7, 2009, 11:00 AM ET

This situation report provides an update to the international situation as of August 4, 2009. World Health Organization (WHO) regions have reported 162,380 laboratory-confirmed cases of novel influenza A (H1N1) and 1,154 deaths. The laboratory-confirmed cases represent an underestimation of total cases in the world as many countries have shifted to strategies of clinical confirmation and prioritization of laboratory testing for only persons with severe illness and/or high risk conditions. The novel influenza A (H1N1) virus is the dominant influenza virus in circulation in the United States, England, South Africa, New Zealand, Australia, Chile, Argentina and Brazil. South Africa has had a notable increase in the proportion of influenza that is novel influenza A (H1N1), and now it represents the majority of influenza in the country. Many seasonal influenza viruses from these countries have not been subtyped. Of those that have been subtyped in Australia, South Africa, and Argentina, the most common seasonal influenza virus is influenza A (H3N2).

Selected Highlights

  • Novel influenza A (H1N1) continues to circulate widely.
  • Descriptive epidemiology of cases remains similar across countries.
  • Isolates sequenced at WHO and CDC suggest that circulating novel influenza A (H1N1) viruses look similar to A/California/07/2009 (the reference virus selected by WHO as a potential candidate for novel influenza A (H1N1) vaccine).

International Resources for Novel H1N1 Information

Health Organizations

World Health Organization (WHO) Regional Offices

Travel and Novel H1N1 Flu

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

Reports and Publications

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