Kate Kelland
Reuters
LONDON: Scientists have used Ebola disease spread patterns and airline traffic data to predict a 75 percent chance the virus could be imported to France by October 24, and a 50 percent chance it could hit Britain by that date.
Those numbers are based on air traffic remaining at full capacity. Assuming an 80 percent reduction in travel to reflect that airlines are halting flights to affected regions, France’s risk is still 25 percent, and Britain’s 15 percent.
“It’s really a lottery,” said Derek Gatherer of Britain’s Lancaster University, an expert in viruses who has been tracking the epidemic.
More than 3 400 people have died since it broke out in west Africa in March and it has now started to spread faster, infecting almost 7 200 people so far. Nigeria, Senegal and now the US – where the first case was diagnosed in a man who flew in from Liberia last week – have all had people carrying the Ebola haemorrhagic fever virus, apparently unwittingly, arrive on their shores.
France is among countries most likely to be hit next because the worst affected countries – Guinea, Sierra Leone and Liberia – are French-speaking, while Britain’s Heathrow is one of the world’s biggest travel hubs.
France and Britain have each treated one national who was brought home with the disease and then cured. The scientists’ study suggests that more may bring it to Europe not knowing they are infected.
Belgium has a 40 percent chance of having the disease arrive on its territory, while Spain and Switzerland have lower risks of 14 percent each, according to the study first published in the journal PLoS Current Outbreaks and now being regularly updated at http://www.mobs-lab.org/ ebola.html.
The World Health Organisation has not placed any restrictions on travel and has encouraged airlines to keep flying to the worst-hit countries. British Airways and Emirates airlines have suspended some flights
But the risks change every day the epidemic continues, says Alex Vespignani, a professor at the Laboratory for the Modelling of Biological and Socio-Technical Systems at Northeastern University in Boston, who led the research.
“This is not a deterministic list, it’s about probabilities – but those probabilities are growing for everyone,” Vespignani said in an interview.
The latest calculations used data from October 1.
“Air traffic is the driver,” Vespignani said.
Patients are at their most contagious when Ebola is in its terminal stages, inducing internal and external bleeding, vomiting and diarrhoea – all of which contain high concentrations of the virus.
But the disease can also have an incubation period of up to 21 days, meaning people can be unaware for weeks that they are infected, and not feel or display any symptoms.
This, it seems, is what allowed the Liberian visitor Thomas Eric Duncanto to fly to the US and spend several days there unaware that he was carrying the deadly virus.
In the EU, free movement of people means someone unknowingly infected with Ebola could easily drive through several neighbouring countries before feeling ill and seeking help, and spend weeks in contact with friends or strangers before becoming sick enough to show up on airport scanners.
Jonathan Ball, a professor of molecular virology at Britain’s Nottingham University, said even with exit screening at airports, the long incubation period meant “cases can slip through the net”.
“Whilst the risk of imported Ebola virus remains small, it’s still a very real risk, and one that won’t go away until this outbreak is stopped,” he said. “Ebola virus isn’t just an African problem.”
However, the chance of the disease spreading widely or developing into an epidemic in a wealthy, developed country is low, health-care specialists say.
“Even if we have a worst case scenario where someone doesn’t present for medical treatment, or it’s not correctly identified as Ebola, and we get secondary transmission, it’s not likely to be a long secondary transmission chain,” Gatherer said.
“People aren’t living in very crowded conditions… It’s a different matter in modern Western cities with the very sanitised, sterile lives that we live.”