Ebola Nigeria WHO Liberia
A female immigration officer uses an infra-red laser thermometer to examine a passenger at Nnamdi Azikiwe International Airport in Abuja, NigeriaReuters

The World Health Organisation (WHO) has urged all countries affected by Ebola to conduct "exit screening" of individuals at all international airports, seaports and major land crossings.

"Affected countries are requested to conduct exit screening of all persons at international airports, seaports and major land crossings, for unexplained febrile illness consistent with potential Ebola infection," a WHO statement on travel and transport in relation to the deadly virus said.

"Any person with an illness consistent with Ebola virus disease (EVD) should not be allowed to travel unless the travel is part of an appropriate medical evacuation. There should be no international travel of Ebola contacts or cases, unless the travel is part of an appropriate medical evacuation."

The countries affected by the disease include Liberia, Sierra Leone, Guinea and Nigeria.

Liberia has the highest death toll from the disease with approximately 400 citizens killed. So far, at least 1,145 people have died from the disease, which has been described as the worst ever outbreak of the virus.

The Kenyan government announced this week that it will ban entry into the country from travellers arriving from Liberia, Guinea and Sierra Leone as it is a major transport hub. The WHO said the high numbers of people travelling through Kenya puts it at "high risk" from the virus.

The highly contagious disease is one of the deadliest in the world and does not yet have a known cure.

The symptoms of the virus include fever, sore throat, diarrhoea and internal and external bleeding, with a 90% fatality rate.