Avian flu or bird flu mainly affects chickens, geese, pigeons, quail and similar domesticated birds. There is also evidence that wild bird populations serve as reservoirs for the virus. The virus can be transmitted directly from fowl to humans leading to serious illness and death. Two characteristics of "bird flu" make it potentially pandemic: (1) it represents a new strain of influenza and (2) people have no natural immune resistance to it. To date it is unproven whether the virus can be transmitted person to person or is solely contracted from direct contact with diseased fowl. The human symptoms of "bird flu" are classic for influenza; sore throat, fever and muscle ache, but can become deadly in the young, elderly or infirm.