The first known emergence of a filovirus happened in August, 1967, in Marburg, Germany.
A shipment of green monkeys from Uganda had arrived in Frankfurt. Green-monkey kidney cells are useful for the production of vaccines, and these monkeys were going to be killed for their kidneys.
Most of the monkeys were trucked from Frankfurt to a factory in Marburg that produced serum and vaccines, while a few monkeys from the same shipment stayed in Frankfurt, and a few others went to Belgrade, Yugoslavia.
The first person known to be infected with the virus—the index case—was a man known as Klaus F., an animal-care technician at the serum factory in Marburg.
He broke with fever and rash on August 8th, and died two weeks later.
So little is known about the Marburg agent that only one book has been published about it, “Marburg Virus Disease,” edited by G. A. Martini and R. Siegert.
In it we learn: The monkey-keeper heinrich p. came back from his holiday on August 13th 1967 and did his job of killing monkeys from August 14th-23rd.
The first symptoms appeared on August 21st. The laboratory assistant renate l. broke a test-tube that was to be sterilized, which had contained infected material, on August 28th, and fell ill on September 4th 1967.
And so on. Thirty-one laboratory workers acquired the disease; seven died. In other words, the case-fatality rate of Marburg virus in hospitalized patients was twenty-two per cent. That was terrifying.
Yellow fever, which is considered a lethal virus, kills only five per cent of the infected once they reach a hospital.
Marburg began with a splitting headache, focussed behind the eyes and temples.
That was followed by a fever. The characteristic diagnostic sign was a red speckled rash over the body which blistered into a sea of tiny white bubbles.
“Most of the patients showed a sullen, slightly aggressive, or negativistic behavior,” Martini wrote. “Two patients [had] a feeling as if they were lying on crumbs.”
One became deranged and psychotic. These mental signs were caused by the virus’s having damaged the brain.
The patient Hans O.-V. showed no signs of mental change, but he suffered a sudden, acute fall of blood pressure and died.
At autopsy, his brain was found to be laced with hemorrhages, and there was a massive, fatal hemorrhage at the center.
In Frankfurt, an animal attendant known as B. developed a high fever and eventually began bleeding from his mouth, nose, and gastrointestinal tract.
He was given whole-blood transfusions, but then he developed uncontrollable hemorrhages at the sites of the I.V. punctures.
He died with blood running from his mouth and his nipples. All the survivors lost their hair. During convalescence, the skin peeled off their faces, hands, feet, and genitals.
It was a small, frightening emergence.
Marburg virus looks like rope, or it rolls up into the rings that resemble Cheerios.
Virologists had never seen a ring-shaped virus, and couldn’t figure out how to classify it. They thought that it might be a type of rabies.
The rabies particle is shaped like a bullet, and if you stretch a bullet it becomes a rod, and the rod can be bent into a doughnut: Marburg. They started calling Marburg “stretched rabies.”
But it is not related to rabies. The question was: What is the virus’s natural history? In what animal or insect does Marburg hide? Marburg evidently does not circulate in monkeys.
Monkeys die quickly of the disease, and if they were the reservoir, Marburg wouldn’t wipe them out.
The monkey’s immune system would have learned to attack the virus, and the virus itself would have become better adapted to living in monkeys without killing them, since it is in the virus’s best interest to let the host survive.
The Marburg monkeys had been collected in Uganda by native trappers—apparently in forested habitat to the west of Mt. Elgon, an extinct volcano that straddles the border between Uganda and Kenya.
Teams of epidemiologists combed Uganda, and especially the western slopes of Mt. Elgon, looking for some animal or insect that harbored Marburg virus; they found nothing.
In 1980, a French engineer who was employed by the Nzoia Sugar Company at a factory in Kenya within sight of Mt. Elgon developed Marburg and died.
He was an amateur naturalist who spent time camping and hiking around Mt. Elgon, and he had recently visited a cavern on the Kenyan side of the mountain which was known as Kitum Cave.
It wasn’t clear where the Frenchman had picked up the virus, whether at the sugar factory or outdoors.
Then, in the late summer of 1987, a Danish boy whose name will be given here as Peter Cardinal visited the Kenyan side of Mt. Elgon with his parents—the Cardinals were tourists—and the boy broke with Marburg and died.
Epidemiologists at usamriid became interested in the cases, and they traced the movements of the French engineer and the Danish boy in the days before their illnesses and deaths.
The result was weird. The paths of the French engineer and the Danish boy had crossed only once—in Kitum Cave. Peter Cardinal had gone inside Kitum Cave.
As for the Ugandan trappers who had collected the original Marburg monkeys, they might have poached them from the Kenyan side of Mt. Elgon. Those monkeys might have lived near Kitum Cave, and might even have occasionally visited the cave.
Mt. Elgon is a huge, eroded volcanic massif, fifty miles across—one of the largest volcanoes in East Africa. Kitum Cave is one of a number of caverns that penetrate Mt. Elgon at an altitude of around eight thousand feet and open their mouths in a deep forest of podo trees, African junipers, African olives, and camphors.
Kitum Cave descends into tight passages and underground pools that extend an unknown distance back into Mt. Elgon. The volcanic rock within Kitum Cave is permeated with mineral salts.
Elephants go inside the cave to root out chunks of salty rock with their tusks and chew on them. Water buffalo also visit the cave to lick the rocks, and they may be followed into the cave by leopards. Fruit bats and insect-eating bats roost in the cave, filling the air with a sour smell.
The animals drop their dung in the cave—an enclosed airspace—and they attract biting flies and carry ticks and mites.
The volcanic rock contains petrified logs, the remains of trees that were enveloped in lava, and the logs are filled with sharp crystals. Peter Cardinal may have handled crystals inside the cave and scratched his hands.
Possibly the crystals were tainted with animal urine or the remains of an insect.
The Army keeps some of Peter Cardinal’s tissues frozen in cryovials, and the Cardinal strain is viciously hot. It kills guinea pigs like flies.
In February, 1988, a few months after Peter Cardinal died, the Army sent a team of epidemiologists to Kitum Cave. The team wore Racal suits inside the cave. A Racal is a lightweight pressurized suit with a filtered air supply, used for hot operations in the field.
There is no vaccine for Marburg, and the Army people had come to believe that the virus could be spread through the air.
Near and inside the cave they set out, in cages, guinea pigs and primates—baboons, green monkeys, and Sykes’ monkeys—and they surrounded the cages with electrified wire to discourage predators.
The guinea pigs and monkeys were sentinel animals, like canaries in a coal mine: they were placed there in the theory or the hope that some of them would develop Marburg.
With the help of Kenyan naturalists, the Army team trapped as many different kinds of wild mammals as they could find, including rodents, rock hyraxes, and bats, and drew blood from them.
They collected insects. Some local people, the il-Kony, had lived in some of the caves.
A Kenyan doctor from the Kenya Medical Research Institute, in Nairobi, drew blood from these people and took their medical histories.
At the far end of Kitum Cave, where it disappears in pools of water, the Army team found a population of sand flies. They mashed some flies and tested them for Marburg. The expedition was a dry hole.
The sentinel animals remained healthy, and the blood and tissue samples from the mammals, insects, arthropods, and local people showed no obvious signs of Marburg.
To this day, the natural reservoir of Marburg is unknown. Marburg lives somewhere in the shadow of Mt. Elgon