Scientists at a top-secret military research unit at Porton Down, Wiltshire, have been assessing the potential use of Ebola as a bioterrorism weapon, according to confidential documents.
A memo, marked UK secret UK eyes only, reveals that the unit, where chemical, radiological and biological threats are analysed, was tasked with evaluating whether terrorist organisations such as al-Qaeda and Isis (Islamic State) could use the deadly virus to attack Western targets.
The heavily redacted document, which has been released under the Freedom of Information Act, reveals that the unit was asked last October to provide "guidance on the feasibility and potential impact of a non-state actor exploiting the Ebola outbreak in West Africa for bioterrorism".
The memo outlines three possible scenarios under which terrorists might seek to exploit the Ebola outbreak, which so far has killed more than 9000 people in the three most affected countries, Guinea, Sierra Leone and Liberia.
The first scenario outlined is completely redacted, illustrating the acute sensitivity about the issue. The second scenario is heavily blacked out but, according to the memo, "would be both logistically and technically challenging for a non-state group to undertake".
A third, also heavily redacted, scenario "constitutes the most technically challenging of the scenarios considered here".
Concerns that terrorist groups might look to "weaponise" Ebola have been raised by several think-tanks and politicians. Last year Francisco Martinez, Spain's state Secretary for Security, claimed that Isis fighters were planning to carry out "lone wolf" attacks using biological weapons. Martinez said that his belief was informed by listening in to conversations uncovered in secret chatrooms used by terrorist cells. The claim has since been played down by others.
Jeh Johnson, the US Department of Homeland Security Secretary, said last October that "we've seen no specific credible intelligence that Isis is attempting to use any sort of disease or virus to attack our homeland".
Dr Filippa Lentzos, a senior research fellow at King's College London and an expert on bioterrorism, said terrorists looking to use the virus as a weapon would encounter problems.
"It doesn't spread quickly at all. Terrorists are usually after a bang and Ebola isn't going to give you that."
Q & A
Could other biological weapons be more attractive to terrorists?
Unlike Ebola, which requires the transmission of body fluids, anthrax spores can be dried and milled to form tiny particles that can be inhaled.
Have pathogens been used as a weapon before?
Following the attacks in New York and Washington in 2001, five people died in the US after opening letters laced with anthrax.
Is there concern that terrorists are becoming increasingly inventive?
One scenario could see terrorists combining genes from different pathogens to synthetically create super pathogens that could spread disease more effectively than Ebola. But expert Dr Filippa Lentzos suggested this was unlikely. "It's pretty damn hard to make dangerous pathogens from scratch in the lab. At this point I'm not sure that's what we need to worry about."