London - Almost $2.9bn was pledged in donations to fight West Africa's Ebola epidemic by the end of 2014, yet only around 40% had actually reached affected countries, researchers said on Tuesday.
A study by the UN Office for the Coordination of Humanitarian Affairs that tracked international donations showed barely $1.09bn had reached the worst affected countries by the end of last year, they said.
"These delays... may have contributed to spread of the virus and could have increased the financial needs," said Karen Grepin, a global health policy expert at New York University who led the study and published it in the BMJ British medical journal.
The West Africa Ebola epidemic, the worst in history, has killed more than 8 800 people since it began more than a year ago, decimating already weak health systems in Guinea, Liberia and Sierra Leone. Its spread now appears to be slowing, especially in Liberia which now has just five cases.
Grepin analysed the level and speed of pledges made to fight Ebola and how they aligned with estimates of funds required to control the epidemic.
She found not only that more than half of funds pledged by international donors had not reached the target countries, but also that global agencies had failed to reliably estimate the amount of money needed.
While Guinea first informed the World Health Organisation of a "rapidly evolving outbreak" of Ebola on 23 March 2014, the first major international appeal was not until August, when some $71m was asked for.
By mid-September 2014, around six months after the epidemic started, the United Nations estimated $1bn would be needed, only to raise that in November to an estimate of $1.5bn.
"Clearly, international leaders have found it challenging to estimate the financial requirements to tackle this rapidly spreading outbreak," Grepin said in a commentary about her findings. "The problem has not been the generosity of donors but that the resources have not been deployed rapidly enough."
UN Ebola chief David Nabarro said last month a further $4bn - equivalent to all aid committed so far - was needed by relief agencies and authorities in the worst affected countries to end the epidemic, with UN agencies alone needing $1bn of that to fund their part in the fight.