National Institute of Allergy and Infectious Diseases (NIAID) http://www.niaid.nih.gov
FOR IMMEDIATE RELEASE Wednesday, April 16, 2008

WHAT:		Do influenza viruses persist in low levels year-round in the northern and southern hemispheres, or does a new crop of the virus emerge afresh in tropical zones such as Southeast Asia before spreading into temperate regions around the globe? Researchers have provided an answer to this long-standing question: new strains arise each year.  The new findings should help public health officials more quickly and accurately determine which strains to include in the annual flu vaccine. The study, supported in part by the National Institutes of Health (NIH), appears online in advance of print in the journal Nature. The researchers analyzed full gene sequences of seasonal influenza virus samples collected from the world’s temperate regions north and south of the equator. Their data comprised full genetic sequences of 1,302 isolates of influenza A virus collected over 12 years from New Zealand and New York state. By quantifying the degree of genetic diversity among the strains’ subtypes, gene segments and geographic locations, the researchers were able to detect patterns indicating that virus strains do not persist from one flu season to the next in the temperate regions. Therefore, the researchers deduced, new flu strains emerge annually from the tropics. The international team of researchers included Jeffery K. Taubenberger, M.D., Ph.D., of the National Institute of Allergy and Infectious Diseases, NIH; Cecile Viboud, Ph.D., of NIH’s Fogarty International Center; and Edward C. Holmes, Ph.D., of Pennsylvania State University, who received funding from the National Institute of General Medical Sciences, NIH. The gene sequence information is stored in an NIAID-supported and publicly accessible database, the Influenza Genome Sequencing Project.
ARTICLE:		A Rambaut et al. The genomic and epidemiological dynamics of human influenza A virus. Nature DOI: 10.1038/nature06945 (2008).
WHO:		NIAID Director Anthony S. Fauci, M.D., is available to comment. Jeffery K. Taubenberger, M.D., Ph.D., Laboratory of Infectious Diseases, NIAID, is also available.
CONTACT:		To schedule interviews, contact the NIAID Office of Communications at 301-402-1663 or niaidnews@niaid.nih.gov.

NIAID is a component of the National Institutes of Health. NIAID supports basic and applied research to prevent, diagnose and treat infectious diseases such as HIV/AIDS and other sexually transmitted infections, influenza, tuberculosis, malaria and illness from potential agents of bioterrorism. NIAID also supports research on basic immunology, transplantation and immune-related disorders, including autoimmune diseases, asthma and allergies.

The National Institutes of Health (NIH)—The Nation's Medical Research Agency—includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov

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