1. Update: influenza activity – United States and worldwide, 2006–07 season, and composition of the 2007–08 influenza vaccine;Centers for disease control prevention;MMWR,2007
2. Stohr K. Influenza. In: David H, editor. Control of communicable diseases manual. 18th ed. Washington; 2004.
3. Centers for disease control and prevention. U.S. outbreak of swine origin influenza A (H1N1) virus infection – Mexico, March–April 2009. [Online 2009, cited 13.05.2010]; Available from: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0430a2.htm.
4. World health organization. World now at the start of 2009 influenza pandemic. [Online 2009, cited 13.05.2010]; Available from: http://www.who.int/mediacentre/news/statements/2009/h1n1_pandemic_phase 6_20090611/en/index.html.
5. World health organization. Weekly update: pandemic (H1N1) 2009 – update 86. Available from: http://www.who.int/csr/don/2010_02_5/en/index.html. [Online 2010, cited 13.5.2010].