„Avian influenza frequently asked questions” (на језику: енглески). World Health Organization. 5. 12. 2005. Архивирано из оригинала 07. 08. 2017. г. Приступљено 13. 2. 2009. „A pandemic can start when three conditions have been met: a new influenza virus subtype emerges; it infects humans, causing serious illness; and it spreads easily and sustainably among humans.”
„Avian influenza frequently asked questions” (на језику: енглески). World Health Organization. 5. 12. 2005. Архивирано из оригинала 07. 08. 2017. г. Приступљено 13. 2. 2009. „A pandemic can start when three conditions have been met: a new influenza virus subtype emerges; it infects humans, causing serious illness; and it spreads easily and sustainably among humans.”