The Ebola virus is "moving faster than we can control it" according to the director-general of the World Health Organisation (WHO).
Margaret Chan told reporters on a telephone briefing from the WHO's Geneva headquarters: "The declaration ... will galvanise the attention of leaders of all countries at the top level. It cannot be done by the ministries of health alone."
She added: "The outbreak is moving faster than we can control it."
The agency said all states with Ebola transmission should declare a national emergency in the face of an outbreak it deemed "particularly serious" but there should be no general ban on international travel or trade.
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