Ebola has plagued four African countries, including Sierra Leona, but where did it come from? These unanswered questions have left scientists puzzled, and finding treatments is a difficult task.

The current Ebola outbreak in West Africa is the worst on record. The virus has infected approximately 3,000, and has killed just about half of that large number. Fears are increasing, as there seems to be no sign of completely eradicating it. 

Scientists are just beginning to learn of the origins of this killer disease, a few months after the initial case was reported in early May. Researchers revealed that they have sequenced the genomes of Ebola from 78 patients in Sierra Leone who contracted the disease in May and June. Those sequences revealed 300 mutations specific to this outbreak, according to Vox.

These analyses can detect the virus' changing behavior and can aid scientists with future diagnostic tests and treatment options.

The virus likely entered Sierra Leone after women became infected when attending the funeral of a traditional healer who had been treating Guinean Ebola patients, Vox reported.

Over time, all viruses mutate, and scientists can use these mutations to understand how Ebola has traveled from person to person. Because they are aware of the virus' general mutation rate, they can also pinpoint the dates of when the disease spread.

Scientists used genetic sequences to locate a common ancestor in Central Africa around 2004, which connects to the recent West African outbreak.

Research further revealed that two different strains of Ebola surfaced from that funeral. Either the healer was infected with two different strains, or another person at the funeral was already infected, according to Vox. When Ebola entered into Sierra Leone, a third strain of the virus appeared.

The disease is hard to distinguish because the symptoms are similar to other illnesses. Only some patients will bleed towards the later stages of the virus' damage.

"My laboratory will be using this sequence information to understand the molecular effects of these mutations," said Erica Ollmann Saphire, Ebola researcher at The Scripps Research Institute in La Jolla, California. "We will also be looking at our pool of antibody therapeutics beyond Zmapp to ensure that candidate cocktails are optimally effective against these circulating strains."

The longer Ebola is infecting people, the more likely it is that the virus will develop a mutation, possibly to the detriment of human health.

The United States will begin the first ever human trials of an Ebola vaccine in September, Vox reported.