The current Ebola outbreak is the worst recorded flare-up in history. More than 700 West Africans have died, and the battle is far from over. Who is really to blame? How about greedy pharmaceutical companies?

Scientists have made great strides in developing an Ebola vaccine, but so far exactly zero candidates have made it past the stage of clinical trials. Vaccines, which require billions of dollars to research and develop, rely on funds from pharmaceutical companies. So despite the fact that many vaccines have made it to the first level of testing, they often can't surpass the intervening hurdles without a big push from private corporations.

Here's the problem: Pharmaceutical companies, for whom decisions must make sense financially, won't take a risk on investing in a vaccine for a disease that only surfaces periodically in low-income countries. Governments and research universities are supposed to help by filling the funding gap. Since that hasn't happened yet, pharmaceutical companies are left to weigh the pros and cons.

In the best case scenario, the disease is cured. If that happens, those who will need it most won't be able to afford an expensive vaccine, so the company won't see a huge profit. In the worst case scenario, the vaccine fails and the company loses money.

"The hang-up point with these vaccines is the phase one trials in humans. That's where scientists get frustrated because we know these vaccines protect animals and we don't quite understand the regulatory process of why things can't move faster," Thomas Geisbert, a virologist in the Department of Microbiology and Immunology at the University of Texas Medical Branch at Galveston who has spent the past two decades studying the Ebola virus, told Scientific American.

Daniel Bausch, a Tulane professor who researches Ebola, agrees. "If you look at the interest of pharmaceutical companies, there is not huge enthusiasm to take an Ebola drug through phase one, two, and three of a trial," Bausch told Vox.

The lack of approved vaccines hasn't stopped some people from getting treated. According to CNN, 33-year old Dr. Kent Brantly of Fort Worth, Texas, who contracted the disease late last month while treating Ebola patients as part of an international relief group called Samaritan's Purse, was recently dosed with an experimental drug called ZMapp, which had so far only been tested on monkeys. Brantly's condition has drastically improved since receiving the experimental drug. Yet his case is hardly the large-scale drug trial companies will need to get full approval for an Ebola vaccine.

Geisbert says we're looking at two to six years minimum before a functioning vaccine becomes available. "I hate to say this, but it really depends on financial support," he said. Hopefully these pharmaceutical companies will wake up soon things will never turned around.