Only decisive action can stop the virus becoming entrenched in Africa and spreading elsewhere, say epidemiologists

Helping hands: troops can train health workers (Image: John Moore/Getty Images)

The world has finally got serious about Ebola. In a first for a public health threat, the United Nations has launched the kind of response it normally reserves for war zones. Meanwhile, the US, UK and France are sending troops to build treatment units, train health workers and keep order.

It’s not a moment too soon: the US Centers for Disease Control and Prevention warn that without a massive effort to slow the epidemic, a million people in West Africa could have Ebola by January. Some will carry it elsewhere, and the virus may circulate non-stop in Africa for the foreseeable future.

In a clear sign that world leaders are worried, the US has earmarked $500 million to fight Ebola, rising to $1 billion if necessary. Whoever pays, the UN says $1 billion will be needed to stop the epidemic, an order of magnitude more than the World Health Organization estimated in July.


The increase reflects the epidemic’s exponential growth: known cases now top 5800, and are doubling every 16 to 30 days. Epidemiologists have known this was coming for months. What has changed is the realisation at the upper levels of the political establishment that Ebola could now have a global impact.

International response

In a reflection of this, the UN Security Council last week called its first-ever emergency meeting on a health threat. It passed a resolution that declared the epidemic “a threat to international peace and security… which unless contained, may lead to further instances of civil unrest, social tensions and a deterioration of the political and security climate”. Margaret Chan, director-general of the WHO, drove the point home, telling the Council: “This is a threat to national security, beyond the outbreak countries.”

At the Security Council’s behest, UN disaster relief experts this week set up a base in Accra, Ghana from which to coordinate international efforts. The UN Mission for Ebola Emergency Response will field military and civilian response teams from China, Cuba, the US, France, the UK and other countries.

Part of the threat if the epidemic continues to grow is the risk to global trade and the integrated financial system. The World Bank estimates that if the epidemic is not substantially slowed, trade and financial disruption could cost West Africa several billion dollars by the end of 2015. “Containment and mitigation expenditures in excess of $1 billion would be cost-effective,” the bank says, if they stop that happening.

The epidemic has already halved economic growth in Guinea, Liberia and Sierra Leone, the three countries most affected. The hardest-hit parts of Liberia and Sierra Leone are key producers of rice, the region’s staple food. Quarantining infected people has interfered with harvests and planting, causing a spike in food prices. In hard-hit Kailahun province in Sierra Leone, 40 per cent of farmers have died or fled.

Worldwide spread

The financial toll, the bank estimates, will kick in big time if Ebola gets loose in more countries. There are precedents. A resurgence of polio in Nigeria in 2003 was carried to Sudan, Saudi Arabia and Indonesia, even though many people are immunised against it.

“If it grows as some models predict to hundreds of thousands of cases by the end of 2014, cases could reach other countries,” says Thomas Inglesby, head of the Center for Health Security at the University of Pittsburgh. “Cities with weak health systems and high populations could have Ebola epidemics that get out of control.” Nearby cities such as Lagos in Nigeria or Kinshasa in the Democratic Republic of the Congo fit the bill, but epidemiologists worry that infected travellers could get much further, as the virus can sometimes take three weeks to produce symptoms. A person who develops symptoms in Calcutta or Mexico City might infect many more people before anyone recognises the disease.

Ian Goldin of the University of Oxford says the US and other rich countries fear Ebola will weaken their trading and strategic partners such as India, Brazil – or Nigeria, also home to Africa’s largest oil reserves, and violent Islamic jihadis. “Threats include extremist takeover, and extremists getting hold of the virus,” says Peter Walsh at the University of Cambridge.

That alone, says Inglesby, warrants calling in the armies of other countries. “For a crisis this big, only the militaries of the world have the logistical, administrative and hospital building expertise to meet the challenge.”

Permanent problem

But even the military may not be thinking big enough. The US plan includes training 500 health workers per week to manage Ebola cases safely. “But this linear increase in the number of workers may be overcome by an exponentially growing number of cases,” says Matthew Hardcastle of the New England Complex Systems Institute. Some of the trainees must become trainers themselves so the number of workers can keep pace.

If efforts to control the epidemic slow, but do not stop its spread, the threat could become permanent. “There is now a high risk that Ebola becomes endemic in West Africa,” says Peter Piot, head of the London School of Hygiene and Tropical Medicine, a co-discoverer of Ebola. This means the virus is always present in people somewhere.

In a major analysis of the data available so far, scientists advising the WHO came to the same conclusion. “We must face the possibility that Ebola will become endemic among the human population of West Africa, a prospect that has never previously been contemplated,” says author Christl Donnelly of Imperial College London (New England Journal of Medicine, doi.org/vvw).

It would then be a continuing source for outbreaks locally and in other countries with poor healthcare systems, says Piot. In theory, a virus just keeps spreading until everyone in reach is exposed and either immune or dead. If a virus like Ebola is not chased out of humans, it will remain a constant threat, racking up a huge toll and limiting free movement – at least until widespread vaccination tames it.

Vaccine trials started last week, and initial observations are promising, but Donnelly and her team warn that it will take many months to scale up production sufficiently to start having an effect on the current epidemic. They calculate that vaccinating only half the people at risk would stop the virus circulating – but unfortunately that now means millions of people.

It might seem easy to stop Ebola reaching the rest of the world: simply stop people flying from infected to uninfected countries (see map above). But the World Bank warns that travel bans would damage the economies of affected countries even more than they have been already. The World Health Organization’s Ebola emergency committee is also against such measures, saying that travel bans impede the movement of healthcare workers and resources, resulting in more cases which itself increases the risk of international spread. The committee says only people exposed to Ebola should be kept from flying – although identifying them is difficult. As Tim Sly of Ryerson University in Toronto, Canada, points out, rich countries have the means to isolate stray cases, but people arriving while incubating the infection may not seek medical care when they first develop symptoms, as Ebola is easily confused with other tropical diseases. And then it may not be correctly diagnosed – allowing the virus to spread. All the more reason for rich countries to redouble their surveillance. Alessandro Vespignani of Indiana University has calculated the chance the virus will emigrate, using a model that combines detailed travel data, incubation times and the rate of increase of the epidemic, with a range of hypothetical, random travel events (PLoS Current Outbreaks, doi.org/vvd). He finds the countries at highest risk are Ghana, the UK and Gambia – and that outside Africa, Belgium, France and the US are also at risk. The model supports the WHO – severe travel restrictions, cutting air traffic to and from the affected region by 80 per cent, would only delay arrival of cases by three to four weeks.

This article appeared in print under the headline “World wakes up to true threat of Ebola”