Showing early symptoms of hemorrhagic fever, the patient sits quietly on her bed, wrangling two toddlers desperate to flee the cell-like hospital room in Ingende, a remote town in the Democratic Republic of the Congo (DRC).
They are waiting for the results of a test for Ebola.

The patient can only communicate with her relatives through a clear plastic observation window. Her identity is secret, to protect her from being ostracized by locals fearful of Ebola infection. Her children have also been tested but, for now, show no symptoms.

There is a vaccine and a treatment for Ebola, which have brought down the rate at which it kills.

But the question at the back of everyone's mind is: What if this woman doesn't have Ebola? What if, instead, she is patient zero of "Disease X," the first known infection of a new pathogen that could sweep the world as fast as Covid-19, but one that has Ebola's 50% to 90% fatality rate?

"Disease X" is hypothetical for now, an outbreak that scientists and public health experts fear could lead to serious disease around the world if and when it occurs, according to WHO. "X" stands for unexpected.

This isn't the stuff of science fiction. It's a scientific fear, based on scientific facts.

"We've all got to be frightened," the patient's physician, Dr. Dadin Bonkole, said. "Ebola was unknown. Covid was unknown. We have to be afraid of new diseases."

Humanity faces an unknown number of new and potentially fatal viruses emerging from Africa's tropical rainforests, according to Professor Jean-Jacques Muyembe Tamfum, who helped discover the Ebola virus in 1976 and has been on the frontline of the hunt for new pathogens ever since.

"We are now in a world where new pathogens will come out," he told CNN. "And that's what constitutes a threat for humanity."

As a young researcher, Muyembe took the first blood samples from the victims of a mysterious disease that caused hemorrhages and killed about 88% of patients and 80% of the staff who were working at the Yambuku Mission Hospital when the disease was first discovered.

The vials of blood were sent to Belgium and the US, where scientists found a worm-shaped virus. They called it "Ebola," after the river close to the outbreak in the country that was then known as Zaire.

The identification of Ebola relied on a chain that connected the most remote parts of Africa's rainforests to high-tech laboratories in the West.

Now, the West must rely on African scientists in the Congo and elsewhere to act as the sentinels to warn against future diseases.

In Ingende, the fears of encountering a new, deadly, virus remained very real even after the recovery of the patient showing symptoms that looked like Ebola. Her samples were tested on-site and sent on to the Congo's National Institute of Biomedical Research (INRB) in Kinshasa, where they were further tested for other diseases with similar symptoms. All came back negative, the illness that affected her remains a mystery.


Speaking exclusively to CNN in the DRC's capital, Kinshasa, Muyembe warned of many more zoonotic diseases -- those that jump from animals to humans -- to come.

Yellow fever, various forms of influenza, rabies, brucellosis and Lyme disease are among those that pass from animals to humans, often via a vector such as a rodent or an insect.

They've caused epidemics and pandemics before.