Ebola: Who is patient zero? Disease traced back to 2-year-old in Guinea By Holly Yan and Lynda Kinkade, CNN

(CNN) -- Before the virus ravaged West Africa, before the deaths soared into the thousands, before the outbreak triggered global fears, Ebola struck a toddler named Emile Ouamouno.

Virtually no one knew the 2-year-old by name. Now the world knows him as patient zero.

Researchers from The New England Journal of Medicine believe Emile was the first person to contract the disease in the current outbreak almost a year ago.

It's not clear exactly how the boy, who lived in a rainforest village in southern Guinea, got infected,

Ebola can be spread from animals to humans through infected fluids or tissue.

"In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines," according to the World Health Organization.

In December, Emile had a fever, black stool and started vomiting. Four days later, on December 6, he was dead.

Within a month, so were his 4-year-old sister, his mother and his grandmother.

The mother suffered bleeding symptoms and died on December 13. Then, the toddler's 3-year-old sister died December 29, with symptoms including fever, vomiting and black diarrhea. The grandmother passed away January 1.

Emile's father is left with only fond memories from before Ebola ripped apart his life.

"Before my children Emile and Philomène died, they loved to play with a ball. My wife liked to carry the baby on her back," Etienne Ouamouno told UNICEF, the U.N. children's agency.

The family lived in the village of Meliandou, where goats and chickens roam around the simple brown huts.

The village sits close to Guinea's borders with Sierra Leone and Liberia.

It didn't take long for Ebola to spread like wildfire.

Like dominoes

The illness spread outside their village after several people attended the grandmother's funeral.

A midwife passed the disease to relatives in another village, and to a health care worker treating her, according to the New England Journal of Medicine.

That health care worker was treated at a hospital in Macenta, about 80 kilometers (50 miles) east. A doctor who treated her contracted Ebola.

The doctor then passed it to his brothers in Kissidougou, 133 kilometers (82 miles) away.

All of them died.

And now, the death toll has skyrocketed to almost 5,000 worldwide, including one in the United States.

The hardest hit, however, are Guinea, Sierra Leone and Liberia.

Lingering effects

In four months after Emile's death, Meliandou buried 14 residents.

The village is now free of Ebola. But the lingering effects there and elsewhere will last for years.

The disease has turned the social fabric on its head. Extended family usually takes orphans in, but fear has broken the chain.

"We noticed that with this crisis, which is almost a humanitarian catastrophe, people flee their villages, and abandon their families and their children," said Fassou Isidor Lama, a UNICEF child protection officer.

"They reject the infected children and the other infected family members."

Then there's the financial toll.

In Meliandou, many of the villagers earned their livelihood selling rice or corn or bananas to nearby towns and cities.

"Nobody wants to buy our products," Amadou Kamano, the village chief, told UNICEF.

Residents, out of fear, also burned their mattresses and other possessions.

"People burned everything," Kamano said. "Now we are even poorer than we were before."

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