The World Health Organization's failure to sound the alarm until months into West Africa's Ebola outbreak was an "egregious failure" which added to the enormous suffering and death toll, global health experts said on Monday.

A specialist panel convened by Harvard's Global Health Institute (HGHI) and the London School of Hygiene & Tropical Medicine (LSHTM) said while the epidemic "engendered acts of outstanding courage and solidarity", it also caused "immense human suffering, fear and chaos" which went "largely unchecked" by leadership or reliable and rapid institutional responses.

Reviewing the global response to the epidemic which swept through Guinea, Sierra Leone and Liberia, the panel said such failures should not be allowed to happen again, and major reform is urgently needed to prevent future pandemics.

"We need to strengthen core capacities in all countries to detect, report and respond rapidly to small outbreaks in order to prevent them from becoming large-scale emergencies," said Peter Piot, LSHTM's director and the chair of the panel.

He said reform of national and global systems to respond to epidemics is not only feasible, but also essential "so that we do not witness such depths of suffering, death and social and economic havoc in future epidemics".

The panel made 10 key reform proposals aimed at preventing future such catastrophes, including developing and investing core capacities to handle infectious disease outbreaks, strengthening incentives for early reporting of outbreaks and science-based justifications for trade and travel restrictions.

It also called for the creation of a unified WHO Center with clear responsibility, adequate capacity, and strong lines of accountability for outbreak response, and for a transparent, politically-protected standing emergency committee to take on responsibility for declaring emergencies.

Liberian panel member Mosoka Fallah of the campaign group Action Contre La Faim International, said the human misery and deaths should prompt serious reflection "on how and why the global response to the greatest Ebola calamity in human history was late, feeble and uncoordinated".

The Ebola epidemic has killed at least 11,300 people in Guinea, Sierra Leone and Liberia since it began in December 2013. The crisis brought already weak health services to their knees and caused social and economic havoc.

"The most egregious failure was by WHO in the delay in sounding the alarm," said Ashish K. Jha, HGHI's director and a leading member of the panel. "People at WHO were aware that there was an Ebola outbreak that was getting out of control by spring, and yet it took until August to declare a public health emergency."

Jeremy Farrar, director of the Wellcome Trust global health charity, said the report had "sobering lessons" which must be learned and "translated into concrete action if we are to avert another crisis".