Almost 40 years after the Ebola virus was identified in humans by scientists in a microbiology laboratory in Belgium, pharmaceutical researchers have yet to develop an effective drug or vaccine to fight it.
Part of the problem is that the deadly virus is rare and its victims are often poor people living in rural areas of Africa without well-functioning health systems. But there is also little incentive for major pharmaceutical companies to invest in medical solutions when there is little chance of a return.
The number of doses sold is likely to be small and many health officials believe the virus and its death toll could be better controlled with good basic hygiene and the eradication of dangerous bushmeat consumption. Yet there is a drug development pipeline, of sorts, out there - mainly funded by the U.S. government which fears such deadly viruses might one day be developed into bioweapons.
"We can do basic research quite cheaply, but when you move from that to trying to develop drugs and vaccines, you get into the need for clinical trials and they are very costly - which is where you would normally start to engage with Big Pharma," said Jonathan Ball, a professor of molecular virology at Britain's University of Nottingham. "And clearly they are not going to invest unless there is likely to be some sort of decent return."
Discovered in 1976 after an outbreak in the Democratic Republic of Congo, then
Zaire, Ebola causes a severe hemorrhagic fever where victims suffer vomiting, diarrhea and both internal and external bleeding.
In an outbreak in Guinea in West Africa, about 86 suspected cases have been reported, with 62 deaths, according to the World Health Organization. Investigations are going on into reported cases in Liberia and Sierra Leone along the border with Guinea.
"Ebola virus is one of the deadliest killers known," said Ben Neuman, a virologist at Britain's University of Reading. "[It] is one of the things that keeps public health officials up at night. If this virus spread between people more easily, it would probably be more deadly than the black plague. Fortunately, up to this point, it has not."
So while for drugmakers there is little commercial future in Ebola, some research groups in the United States are working in conjunction with the U.S. government to find treatments.
In March, the University of Texas and three other organizations got $26 million in funding from the U.S. National Institutes of Health to find a cure for Ebola and another deadly virus Marburg in case they are ever used for bioterrorism in the United States.
Tekmira Pharmaceuticals, which teamed up with the U.S. Department of Defense on an injectable drug treatment for Ebola, started an initial Phase I trial in healthy volunteers in January.
Several small biotech companies and U.S. university departments are also developing potential vaccines, but this work has yet to advance from animal studies into clinical trials in humans - so any use in people now would be very risky.
U.S.-based Inovio and privately held Vaxart are among those with experimental vaccines in animal testing, while GlaxoSmithKline last year acquired Swiss vaccine firm Okairos with an early-stage Ebola product.
"There are a few experimental vaccines, but the question is whether anybody would take on the costs of manufacture based on the likely number of doses they would eventually sell," said Ian Jones, a professor of virology at Reading University. "The numbers of people infected are low, and at the end of the day somebody has to fund the production of a drug or vaccine. As things stand that is unlikely."
The immense difficulty and high cost of conducting human clinical trials for a potential drug or vaccine are prohibitive, experts point out, since Ebola cases are generally far-flung, rare and unpredictable.
"For a start there are simply not enough patients and you wouldn't know when the next outbreak was going to happen," said Jones. "Even then you couldn't guarantee there would be enough people to run a trial. Which means you would have to go from the best evidence in animal models."
Some scientists say the current outbreak in Guinea could be an opportunity to do just that - offering a chance to push the field forward and test potential vaccines or drugs.
Thomas Geisbert at the University of Texas Medical Branch is working on a vaccine known as vesicular stomatitis virus-based Ebola vaccine, or VSV, which he said had shown 100 percent efficacy in tests on animals.
The shot, which has not gone through clinical trials in humans, could, he said, be issued on "compassionate grounds" to people in Guinea at risk in the current Ebola outbreak.
"You have to reach a balance between advancing science, medical ethics and saving lives," he told Reuters. "It's not easy, but how many people faced with the prospect of near certain death would opt to take their chances with the virus?"