In an era when the next pandemic can seem just a pathogen away, Ebola still retains a grisly fascination. The disease has a heart of darkness reputation - it was identified in 1976 in the Democratic Republic of Congo, then Zaire, a despotism even Joseph Conrad may have baulked at.

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And Ebola has a grisly endgame. About half of its victims bleed to death as the virus eats tiny holes in capillaries and blood vessels, so that blood steadily seeps out, even from the eyes. Others die after violent vomiting and diarrhoea.

This fate appears to have been the case with Patrick Sawyer, 40, a Liberian official and United States citizen who fell sick in the air en route to Lagos, after flying from Monrovia, the capital of Liberia, via Tome, the capital of Togo. Upon arrival in Lagos he collapsed. Sawyer was taken to a private hospital, then a government facility where he died in quarantine on the night of July 24.


It was Nigeria's first Ebola case. The hospital has been closed and staff isolated.

His death raised the terrifying prospect of Ebola's presence in Africa's largest city, home to 21 million. Ebola has a two to 21-day incubation period. So far, there are no reports of secondary infections. Lagos may have dodged a bullet.

But in a sprawling, world-connected megalopolis, infamous for poverty, homelessness, overcrowding, corruption and lawlessness, all bets are off.

As local media depicted a city in the grip of fear, airports stepped up surveillance and airlines cancelled flights to infected regions, officials were still trying to contact anyone with whom Sawyer had contact, including 35 passengers who Daily Newswatch says have gone to ground.

"There's no secondary transmission in Lagos that I know of," says Laurie Garrett, a senior fellow for global health at the Council on Foreign Relations and author of The Coming Plague.

"If there is, and they have Ebola spreading on the ground between Nigerians, then all hell's going to break loose. "

Over the past five months Ebola has scythed through Guinea, Liberia and Sierra Leone, killing upward of 729 as of July 27. If past outbreaks are any guide, the host for West Africa's epidemic, first detected in Guinea's remote Nzerekore region in February, was likely a fruit bat, a local bushmeat delicacy. Or it may have been another creature, perhaps a monkey; bats masticate fruit, dropping bits on the rain forest floor, where creatures eat it, absorbing saliva.

Fears Ebola may go global - up to 90 per cent of victims die - lurk just below the surface. Western leaders seemed nervous. This week British Prime Minister David Cameron said the outbreak was a "very serious threat" to the UK, the US said Ebola was a plane ride away and Public Health England warned doctors and hospitals to be vigilant.

Events have escalated sharply this week. As the mortality rate shot up, Medecins San Frontieres - which has staff on the front line - said the epidemic was out of control, the US withdrew Peace Corps volunteers, the Centre for Disease Control advised travellers to avoid the region, and Liberia and Sierra Leone declared states of emergency, closing schools and markets and ordering civil servants to stay home as villages are quarantined.

The World Health Organisation announced a US$100 million ($117.6 million) fightback fund, in part to prevent the outbreak from spilling over to other nations - a very real possibility in remote rainforest regions where borders are porous.

It takes a special kind of courage to battle Ebola. Healthcare workers must wear hazmat suits, complete with respirators, masks and gloves.

Even then they risk death. This week Sheik Umar Khan, 39, a doctor battling the outbreak in Sierra Leone, died. Samuel Brisbane, a prominent Liberia doctor, died days earlier. Two American medicos, Dr Kent Brantly and Nancy Writebol, were infected in Monrovia. Both are in quarantine.

While prototype vaccines exist none have been marketed to fight the pathogen virologists describe as a "molecular shark". Clinical trials are hard to devise without background communities to test any drug for efficacy and side effects.

Peter Piot, the Belgian scientist who helped find the virus, said it was time to try prototypes on Ebola patients, a sign of desperation as the outbreak, far worse than any of its predecessors, with 1323 confirmed and suspected cases, rages out of control. Responders rely on palliative care; quarantining and rehydrating victims and removing bodies. The virus is passed via bodily fluids or infected surfaces, such as sheets, through broken skin and mucous membranes. Victims are contagious when symptoms appear. But early signs like headaches, muscular pain and fever are common to many endemic diseases, including malaria.

Past outbreaks, including one Garrett experienced in Kikwit, Zaire, in 1995, were rural and easily contained. This time the outbreak is both rural and urban. It is also the first to cross national borders, posing immense challenges of co-governance, co-control and mutual agreement in three nations that rank among the world's poorest.

Both challenges are amped up by a third factor; deep trauma from back-to-back civil wars in Liberia and Sierra Leone (Guinea was as a staging post) between 1985 and 2003.

Child soldiers hacked limbs off, people were publicly tortured, some were burned alive and hundreds of thousands were killed and displaced in an orgy of violence.

No one remains untouched by the horrors, says Garrett. "This has left the people deeply scarred and deeply suspicious of anybody that isn't their own. You come from another village and you're a suspect. But you come in with white skin wearing a space suit? Hello."

Rumours of doctors practising cannibalism or chopping off limbs - horrors rampant in the wars - are proving almost as redoubtable in some areas as Ebola.

People have raided hospitals to take back infected family members.

"We're forgetting what these people have been through," says Garrett. "The main way of controlling Ebola is to take your loved one away from you. And in most cases you never see them again and you won't be allowed to give them a funeral."

Healthcare workers have been attacked, vehicles stoned. Nor does it help that many locals are illiterate and have no idea what a virus or germ is.

To many, the outbreak is retribution from the spirit world for evil deeds dating from the wars, as people ask shamans to conjure up evil spirits as payback against enemies. Aid efforts are complicated by belief systems like this, including burial rites where people touch the dead - Sierra Leone was infected when a healer crossed a border to perform last rites, bringing Ebola home afterwards.

The outbreak is another cruel blow to the region. While epidemiological and molecular evidence from patients suggests human-to-human transmission, why Ebola surfaced in West Africa is unclear.

"While there are a few small differences to the genetic code found in past outbreaks, this one closely resembles the same species of virus that has been found in Central Africa," says Barbara Knust, an epidemiologist in the CDC's Viral Special Pathogens Branch. She speculates the virus may have been present but undetected.

Fruit bats seem likely hosts. Common in rainforests that stretch across the continent, they migrate over vast areas for food. At the same time many diseases - Ebola, Mers, Sars, Lyssavirus and others - have been traced to bats, which appear immune and may have hosted such viruses for millennia.

When they jumped to humans is unclear. But something has gone wrong in the forest. Bats are under great stress around the world, hurt primarily by two threats: habitat loss and climate change. Combined with globalisation, both remain serious obstacles to containing zoonotic epidemics.

Meanwhile, the fightback may be just beginning, although frontline care has kept the mortality rate at around 60 per cent. "The response to this outbreak will be more of a marathon than a sprint," Steve Monroe, Director of the CDC's National Centre for Zoonotic and Infectious Diseases, told journalists this week. He warned of more cases.

According to Pierre Formenty, the WHO's Ebola expert, the outbreak surged after efforts to halt the pathogen were relaxed when the outbreak seemed to be winding down in April.

Garrett fears the world will isolate infected nations, who need help building basic health services. The death of even a handful of doctors is a crippling blow.

Outside responders must win community trust, enlisting local leaders as intermediaries. But that opportunity may have passed as the Ebola outbreak spreads. "If that had been done in a strategic way, with large-scale support from wealthy countries, so that it could be done right, and done fast and thoroughly, we might not be in the situation we're in now. Now it's too late."