Ebola crisis: Speed and extent of outbreak 'unprecedented' Published duration 22 August 2014

image copyright AP image caption Food was distributed in the West Point area of Monrovia, where some residents have expressed anger over a quarantine

The World Health Organization has said the speed and extent of the Ebola outbreak in West Africa is "unprecedented".

The WHO's Dr Keiji Fukuda expressed concern over so-called "shadow zones", areas which cannot be reached and where patients are not being detected.

The organisation confirmed 142 new cases of the disease had been reported since 19 August, as well as 77 deaths.

Already more people have died in this outbreak of Ebola than in any other.

At least 1,427 people have now died in the outbreak so far, with the number of cases now standing at 2,615.

Speaking at a news conference in the Liberian capital Monrovia, Dr Fukuda said combating the disease would take "several months of hard work".

"We haven't seen an Ebola outbreak covering towns, rural areas so quickly and over such a wide area," he added.

Also on Friday, Nigerian authorities said that they had detected two new cases of the virus, both spouses of medical workers who had direct contact with a man who died from the virus in Nigeria after arriving from Liberia.

In Liberia on Friday, a boy of 16 shot during a protest about a quarantine died.

Shakie Kamara was one of three people seriously injured on Wednesday after security forces fired at protesters, angry after blockades were erected around the West Point slum.

image copyright AFP image caption The WHO has said more medical resources are needed to halt the spread of the virus

WHO says Ebola outbreak underestimated because:

Many families keep sick people at home, as there is no cure

Many health centres have closed because medical staff have fled

In Liberia, treatment centres are overwhelmed

The existence of "shadow-zones", areas where there are reports of Ebola but which cannot be accessed because of local resistance or lack of staff

Meanwhile, Senegal has defended the closure of its border with Guinea because of the Ebola outbreak, despite warnings that such measures are counterproductive.

The WHO says travel bans do not work, and that what is needed is more doctors and officials to help trace those infected with Ebola, and more mobile laboratories.

Senegal also banned flights and ships from Guinea, Liberia and Sierra Leone - the three worst-hit countries - however, Senegal's Health Minister Dr Awa Marie Colle Seck said humanitarian flights would not be affected.

Cameroon, Ivory Coast, Kenya and South Africa have also imposed travel bans.

Ebola has no known cure but some affected people have recovered after being given an experimental drug, ZMapp. However, supplies are now exhausted.

On Thursday, two US doctors were discharged from hospital after being given the drug, while three Liberian medics are also recovering well.

Ebola Virus Disease (EVD)

image copyright Getty Images image caption Fruit bats are believed to be a major carrier of the Ebola virus but do not show symptoms