Kikwit, Zaire -- The Foret Pont Mwembe is a curious bit of forest.

Densely packed with tiers of lush greenery, it flickers with a rainbow of breathtaking butterflies. But it has none of the sounds typically heard in African forests -- the cooing and screeching of monkeys, chimpanzees or gorillas. No antelopes lap at the streams. Few tropical birds dart among the verdant trees.

"It's a jungle," says Robert Swanepoel, the virologist leading the search for the animal source of the Ebola virus. "Nobody lives there. And the forest seems virtually lifeless," all large animals having long since been hunted to extinction.

Local hunters "must now satisfy themselves with catching mice, rats, mongoose, hedgehogs, and snakes," says Christophe Giseszele, a Kikwit biology student who showed the area to a visitor ten days ago. "Everything else is gone."

To this forest, Gaspard Menga came each day, traveling 18 miles, from his small Kikwit home to gather wood, burn it into charcoal and sell the blackened strips as fuel back in the city of Kikwit. His journeys ended in January when he died -- the first case, it is thought, of Ebola in the Kikwit epidemic.

And it is here that scientists have come to trap mice, rats and bats so their blood and tissues can be analyzed for Ebola infection. By figuring out how Menga got Ebola, Swanepoel and his colleague are hoping to find the answer to a 19-year-old mystery: Where does the Ebola virus reside when it is not killing humans?

Probably not in insects. They are abundant everywhere in the Kikwit region, but if they carried Ebola, the disease would be far more common and less clearly confined to person-to-person transmission.

Some residents of Kikwit keep pet monkeys, chimps and gorillas. But careful investigation by Dr. Oyewale Tomori of the World Health Organization and Dr. Scott Dowell of the U.S. Centers for Disease Control and Prevention has found no Ebola cases among the pet owners, their neighbors or families.

Still, the scientists have drawn blood from the angrily protesting animals, which are being analyzed in Swanepoel's makeshift virology lab, in the former tuberculosis clinic of Kikwit General Hospital.

It would make sense if the culprit turned out to be a rodent, experts say. Most of the other hemorrhagic fever viruses are carried by rats, bats or mice, possibly because rodents^ blood-clotting mechanisms may render them less likely to suffer uncontrolled bleeding from the viruses. Bolivian hemorrhagic fever, for instance, is caused by the Machupo virus, from wild mice. The deadly Lassa virus found in west Africa lives in rats. And rats or mice carry all the hantaviruses -- including the strains that struck the American Southwest in 1993 and killed two people on Long Island since then.

On a recent day, working inside a respirator bodysuit to protect himself from the deadly virus, Swanepoel analyzed blood samples drawn from bats captured in Kikwit's largest Catholic church. He mixes antibodies against Ebola -- drawn from surviving patients -- with chemicals that emit florescent light and adds them to the blood samples. If Ebola is there, the fluorescent antibodies will latch onto the viruses, creating an image Swanepoel can clearly see with a standard microscope -- except when the hood of his overheated plastic suit fogs up in the heat.

"A bit like being wrapped in Saran Wrap," Swanepoel says of the gray plastic gear.

Swanepoel and his colleagues sense that they are closer to learning what animal carries Ebola than any previous research team has been. And nothing -- certainly not the sweltering discomfort of his spacesuit -- can keep him from the hunt.