The number of deaths from the ebola virus in west Africa has surpassed 1,900, more than all previous outbreaks combined, according the World Health Organisation.

Statistics from the Geneva-based UN health agency show that in 24 earlier outbreaks, including the first in 1976, 1,590 people died.

The WHO Director General Dr Margaret Chan said  "there were 3,500 confirmed or probable cases in Guinea, Sierra Leone and Liberia and the outbreak is rising,"

The latest toll represents a significant increase from the 1,552 deaths and 3,069 cases reported by the WHO just days ago.

Speaking at a news conference, Dr Chan said she hoped that, thanks to the global response to the crisis, transmission of the often fatal virus could be stopped in six to nine months.

Citing the WHO's roadmap to fight the worst Ebola outbreak in history, she said that in countries with "very intense transmission, we would like to reverse the trend in three months."

She said for countries with "localised transmission" such as the Democratic Republic of Congo and Senegal, the WHO "would like to stop all transmission within eight weeks."

In response to the current crisis, the WHO held a meeting today to discuss how to fast-track the testing and production of the most promising treatments to tackle the outbreak in west Africa.

The WHO called on pharmaceutical companies and regulatory agencies to work together to accelerate development of safe and efficient drugs and vaccines against the disease.

Ten experimental treatments - eight drugs and "two promising candidate vaccines" - have shown potential against the virus but remain under investigation, the WHO said in a document distributed at the start of the two-day meeting in Geneva.

They include the anti-body drug ZMapp made by US-based MappBiopharmaceutical Inc, which has been given to several patients with Ebola for "compassionate care" but whose clinical effectiveness is "still uncertain", it said.

"Efforts to scale up production (of ZMapp) may yield increased supplies of potentially a few hundred doses by the end of 2014."

Evidence of the effectiveness of the medicines and vaccines is "suggestive but not based on solid scientific data from clinical trials," the WHO said. Existing supplies of all experimental medicines are extremely limited or exhausted.

'Ebola is spreading at an ever greater rate'

The outbreak of Ebola in Sierra Leone is not under control and the situation is deteriorating, according to an Irish doctor who has just returned from the region.

Doctor Gabriel Fitzpatrick has just returned to Europe from Sierra Leone where he was working with Medecins san Frontieres.

Speaking on RTÉ's Morning Ireland, Dr. Fitzpatrick said he discovered new clusters of the disease on a daily basis while he was there.

"Basic elements of outbreak control in that region of the world are not being met at the moment and that is, finding cases early, bringing those cases to Ebola treatment centres and following up on contacts of those cases so I have to say at the moment that's not being done and as a consequence we are seeing the Ebola virus spread at an ever greater rate."

Fears of virus spreading further

The arrival of the virus in Nigeria's oil producing port has sparked concerns of accelerated transmission.  

The virus first arrived in Nigeria when a Liberian finance ministry official died in Lagos on 25 July. 

WHO said the arrival of the virus in Port Harcourt, which is 435 kilometres east of Lagos, showed "multiple high-risk opportunities for transmission of the virus to others".

Ebola has hit five countries in West Africa and has caused nearly 2,000 deaths this year.