Scientists have come up with the likely possibility of how Ebola's first victim — Patient Zero — contracted the deadly disease that has ravaged parts of West Africa.

Patient Zero, who has since been identified as two-year-old Guinean Emile Ouamouno, may have been infected while hunting or playing with bats inside a hollow tree near his home in a small village named Meliandou, according to researchers. He died in December 2013.

Research published in the EMBO Molecular Medicine journal finds that the single transmission, from bat to boy, was then spread human to human.

Since the epidemic began, scientists have not been able to determine the cause, though many believe fruits bats were a "natural reservoir" of the virus, according to the World Health Organization

Meliandou Ebola first case

The village of Meliandou in southeastern Guinea, where the current Ebola outbreak first began. (EMBO Molecular Medicine)

The EMBO study has expanded the range of possible Ebola sources to include insectivorous bats — the species that were in and around the hollow tree where Ouamouno played. Insectivorous bats have previously been discussed as potential Ebola sources, and the study says "experimental data have shown that this species can survive experimental infection​."

Researchers are also leaning more toward insectivorous bats because they found no large colony of fruit bats near Meliandou.

The scientists arrived at this assumption during a four-week field mission in southeastern Guinea in April, just after the virus broke out. They examined human exposure to bats and other bushmeat, surveyed local wildlife in the forests surrounding the area, and captured and sampled bats in the Meliandou area as well as in neighbouring forests. 

Study rules out bushmeat

Over eight days, scientists carefully observed the boy's village and spoke with villagers to determine how the boy contracted Ebola. Meliandou is a small village of 31 houses, surrounded by farmland and few larger trees.

Villagers said children used to play frequently in a hollow tree about 50 metres from the boy's home, which housed a colony of insectivorous bats. In the report, villagers said the tree burned down on March 24, and when it caught fire, a "rain of bats" started. A large number of them were collected to eat. 

Meliandou tree stump Ebola first case

The stump of the hollow tree where two-year-old Emile Ouamouno was likely infected with the Ebola virus while hunting or playing with bats. (EMBO Molecular Medicine)

The researchers didn't find evidence of Ebola transmission from the consumption of the bats, but villagers said they disposed of them after a ban on bushmeat was announced the following day. 

The study determined Ouamouno's interaction with bats is the likely cause of transmission by ruling out other possibilities, namely that the virus was spread by the consumption of bushmeat.

"Would contaminated fresh bushmeat have been brought to the village by a hunter, the [hunter] would likely be among the first cases, as observed in several outbreaks in the Congo Basin," reads the study.

"However, only children and women presented symptoms or died in the beginning of the current epidemic, and the sole survivor of the index case's family is the father, who had not lived in household for several years and was reported never to have been a hunter."