Peter Piot, the Belgian scientist who co-discovered the Ebola virus in 1976, on Tuesday said a "perfect storm" in West Africa had given the disease a chance to spread unchecked. "We have never seen an (Ebola) epidemic on this scale," Piot was quoted by the French daily Liberation as saying. "In the last six months, we have been witnessing what can be described as a 'perfect storm' -- everything is there for it to snowball." The epidemic "is exploding in countries where health services are not functioning, ravaged by decades of civil war," Piot said. "In addition, the public is deeply suspicious of the authorities. Trust must be restored. Nothing can be done in an epidemic like Ebola if there is no trust." Piot is former chief of the UN agency UNAIDS and now director of the London School of Hygiene and Tropical Medicine, one of the world's foremost centres of expertise on tropical disease. In the interview, he also castigated "the extraordinary slowness" of international organisations in responding to the outbreak. "The World Health Organization (WHO) only woke up in July," whereas the epidemic began in December last year and health experts sounded the alarm in early March, said Piot. "There is now leadership but it is late," he said. The epidemic has killed 1,427 people out of more than 2,600 known cases of infection, with doctors and nurses paying a particularly heavy price. The epidemic is focussed on Liberia and Sierra Leone, which were wracked by conflict in the 1990s and the early part of the last decade, and on neighbouring Guinea. Other cases have been recorded in Nigeria, whose north is hit by unrest, and in the Democratic Republic of Congo, whose east is in the grip of a decades-old conflict and where Ebola was first identified in 1976. DRC Health Minister Felix Kabanga Numbi last Sunday said that the country's seventh recorded Ebola outbreak had "no link to (the epidemic) in west Africa". Here is a recap of the worst Ebola epidemics since the deadly virus appeared in Africa nearly 40 years ago. There have been more than 20 outbreaks since then. -- 1976 -- The Ebola virus was first identified as it spread simultaneously across two regions along the border between Sudan and what was then Zaire, now the Democratic Republic of Congo (DRC). The haemorrhagic fever takes its name from a river in the area. The worst outbreak killed 280 people in DRC, out of 318 known cases in that country. In Sudan, 151 people died out of a total of 284 identified cases. -- 1995 -- The DRC was hit again by the virus, in this case by the type known as Ebola Zaire, which infected 315 people, killing 254 of them. The epidemic was centred in the western Kikwit region. A doctor testified that a nurse contracted the virus simply by closing the eyes of someone who had just died. -- 2000/2001 -- Uganda was affected for the first time as the Ebola Sudan strain ravaged two parts of the country, mainly the northern city of Gulu, but also the Masindi district and the southwestern town of Mbarara. From September 2000 until February 2001, the fever killed 224 people of the 425 who were infected. -- 2001/2002 -- In Gabon, the Ebola Zaire strain spread between October 2001 and May 2002 in the northeastern province of Ogooue-Ivindo, killing 53 victims among the 65 identified cases. It was the fourth time this sparsely populated equatorial region was affected, and the virus also killed 44 people in neighbouring Republic of Congo. Previous Ebola epidemics in Gabon, one in 1994 and two in 1996, left around 100 people dead. -- 2003 -- The Ebola Zaire strain struck the Republic of Congo again between January and April, killing 128 people of the 143 who were infected, for a mortality rate of 90 percent. The virus was particularly virulent in the western Cuvette-Ouest region, near the border with Gabon among those who handled the carcasses of forest gorillas and chimpanzees that had perished from the virus. In October 2003, another outbreak of the same species killed 29 more people. -- 2007 -- Once again, it was the Ebola Zaire species that killed 187 people in DRC among a total 264 identified cases. The haemorrhagic fever struck mainly between April and October in the central Kasai occidental region. A year later, and again in 2012 the virus hit DRC, killing 73 people. -- 2014 -- Ebola was identified for the first time in west Africa, first in Guinea, then in neighbouring Liberia and Sierra Leone, before it was reported in Nigeria. The epidemic has killed 1,427 people out of more than 2,600 known cases of infection, according to the UN World Health Organization. The DRC also faced its seventh outbreak in August, said by the health minister to be separate from the west African epidemic.