Tracing an Epidemic’s Origins

As is often the case in Ebola outbreaks, no one knows how the first person got the disease or how the virus found its way to the region. The virus infects monkeys and apes, and some previous epidemics are thought to have begun when someone was exposed to blood while killing or butchering an infected animal. Cooking will destroy the virus, so the risk is not in eating the meat, but in handling it raw. Ebola is also thought to infect fruit bats without harming them, so the same risks apply to butchering bats. Some researchers also think that people might become infected by eating fruit or other uncooked foods contaminated by droppings from infected bats.

Once people become ill, their bodily fluids can infect others, and they become more infectious as the illness progresses. The disease does not spread through the air like the flu; contact with fluids is necessary, usually through the eyes, nose, mouth or cuts in the skin. One drop of blood can harbor millions of viruses, and corpses become like virus bombs.

A research team that studied the Guinea outbreak traced the disease back to the 2-year-old who died in Guéckédou and published a report in The New England Journal of Medicine. He and his relatives were never tested to confirm Ebola, but their symptoms matched it and they fit into a pattern of transmission that included other cases confirmed by blood tests.

But no one can explain how such a small child could have become the first person infected. Contaminated fruit is one possibility. An injection with a contaminated needle is another.

Sylvain Baize, part of the team that studied the Guinea outbreak and head of the national reference center for viral hemorrhagic fevers at the Pasteur Institute in Lyon, France, said there might have been an earlier case that went undiscovered, before the 2-year-old.

“We suppose that the first case was infected following contact with bats,” he said. “Maybe, but we are not sure.”