Spillover

by David Quammen

  Joosten’s husband, later her widower, was a fair-skinned man named Jaap Taal, a calm fellow with a shaved head and dark, roundish glasses. Most of the other travelers didn’t fancy this offering, Jaap Taal told me, over a cup of coffee at a café in southwestern Montana. Never mind, for the moment, why he turned up there. Python Cave had been an add-on, he explained, price not included in their Uganda package. “But Astrid and I always said, maybe you come here only once in your life, and you have to do everything you can.” They rode to Maramagambo Forest and then walked a mile or so, gradually ascending, to a small pond. Nearby, half-concealed by moss and other greenery, like a crocodile’s eye barely surfaced, was a low dark opening. Joosten and Taal, with their guide and one other client, climbed down into the cave.

  The footing was bad: rocky, uneven, slick with bat guano. The smell was bad too: fruity and sour. Think of a dreary barroom, closed and empty, with beer on the floor at 3 a.m. The cave seemed to have been carved by a creek, or at least to have channeled its waters, and part of the overhead rock had collapsed, leaving a floor of boulders and coarse rubble, a moonscape, coated with guano like a heavy layer of vanilla icing. The ceiling was thick with bats, big ones, many thousands of them, agitated and chittering at the presence of human intruders, shifting position, some dropping free to fly and then settling again. Astrid and Jaap kept their heads low and watched their step, trying not to slip, ready to put a hand down if needed. “I think that’s how Astrid got infected,” he told me. “I think she put her hand on a piece of rock, which contained droppings of a bat, which are infected. And so she had it on her hand.” Maybe she touched her face an hour later, or put of piece of candy in her mouth, or something such, “and that’s how I think the infection got in her.”

  Python Cave, in Maramagambo Forest, is just thirty miles west of Kitaka Cave. It too harbors Egyptian fruit bats. Thirty miles isn’t far and individuals from the Kitaka aggregation are quite capable—as the CDC team’s mark-recapture study would later prove—of finding their way to roost at Python.

  No one had warned Joosten and Taal about the potential hazards of an African bat cave. They knew nothing of Marburg virus (though they had heard of Ebola). They only stayed in the cave about ten minutes. They saw a python, large and torpid. Then they left, continued their Uganda vacation, visited the mountain gorillas, did a boat trip, and flew back to Amsterdam. Thirteen days after the cave visit, home in Noord-Brabant, Astrid Joosten fell sick.

  At first it seemed no worse than flu. Then her temperature went higher and higher. After a few days, she began suffering organ failure. Her doctors, knowing her case history, with recent time in Africa, suspected Lassa virus or maybe Marburg. Marburg, said Jaap, what’s that? Astrid’s brother looked it up on Wikipedia and told him: Marburg virus, it kills, could be bad trouble. The doctors moved her to a hospital in Leiden, where she could get better care and be isolated from other patients. There she developed a rash and conjunctivitis; she hemorrhaged. She was put into an induced coma, a move dictated by the need to dose her more aggressively with antiviral medicine. Before she lost consciousness, though not long before, Jaap went back into the isolation room, kissed his wife, and said to her, “Well, we’ll see you in a few days.” Blood samples, sent to a lab in Hamburg, confirmed the diagnosis: Marburg. She worsened. As her organs shut down, she lacked for oxygen to the brain, she suffered cerebral edema, and before long Astrid Joosten was declared brain-dead. “They kept her alive for a few more hours, until the family arrived,” Jaap told me. “Then they pulled the plug out and she died within a few minutes.”

  The doctors, appalled by his recklessness in kissing her goodbye, had prepared an isolation room for Jaap himself, but that was never needed. “There’s so much they don’t know about Marburg and those other viral infections,” he said to me. Then, still a venturesome traveler, he went off on a snow tour of Yellowstone National Park.

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  The news of Astrid Joosten’s death carried far. She was the first person known to have left Africa with an active filovirus infection and died. The Swiss graduate student from Côte d’Ivoire, back in 1994, had recovered. Did any other person, apart from those two, ever pass through an international airport and depart the continent with Ebola or Marburg virus incubating in his or her body? No one of whom the experts were aware. Joosten’s case proved that Marburg could travel in a human, though admittedly it didn’t travel so well as SARS or influenza or HIV-1. Five thousand miles away, in Colorado, another woman heard the news with a shudder of recognition. She had visited Python Cave too.

  Michelle Barnes is an energetic late-fortyish woman with blue eyes and auburn hair, one sibling among seven from an Irish Catholic family in Iowa. She’s an avid rock climber and bicyclist, a camper and hiker, who has worked for Outward Bound in the past and now serves as an interim executive (stepping in when needed during transitions) and troubleshooter for nonprofit organizations. On the day I met her, at an office in downtown Boulder, she wore a red sweater and a scarf and looked healthy and professional. The auburn, she told me cheerily, came from a bottle. It approximates the original color, she said, but the original is gone. In early 2008 her hair started falling out; the rest went gray, “pretty much overnight.” This was among the lesser effects of a mystery illness that had nearly killed her, during January that year, just after she’d returned from Uganda.

  Her story paralleled the one Jaap Taal had told me about Astrid, with several key differences—the main difference being that Michelle Barnes was still alive. Another was that her case showed how hard it could be to get correctly diagnosed. Michelle and her husband, Rick Taylor, who runs a construction company, were entranced with Africa, like Jaap and Astrid. They too had made earlier trips, usually traveling to remote places on their own. And they too, this time, wanted to see mountain gorillas. So they booked with an adventure-travel outfitter, because those companies control permits for visiting the gorillas. Their itinerary had them progressing southward through the landscape attractions of western Uganda, again as Jaap and Astrid would later do, leaving the big apes down in Bwindi to be a crescendo near the end of the trip. One intermediate stop was Queen Elizabeth National Park, along the east shore of Lake Edward. It was a drier and flatter ecosystem, offering classic East African savanna full of lions and elephants and other big mammals, which converge on the water holes around dawn and dusk. Midday at Queen Elizabeth, blazing hot and bright, tends to be an off time for viewing wildlife. So on one of the days there, with about five hours to kill, the guide announced that they would go see a cave. Change of pace from the lions and elephants: pythons and bats.

  Barnes and her group walked the same mile through Maramagambo Forest and entered the same cave, crossing an irregular floor of large rocks besmeared with guano, which made for poor footing. The walls were acrawl with large, hairy spiders, by her recollection. The ceiling was low and the roosting bats dangled down within two or three feet of a person’s head. Some bats flew in and out, screeching as they went. The stench was ammoniac and horrible. You had to clamber across those slippery boulders. As a rock climber, Barnes said, she tends to be very conscious of where she places her hands. No, she didn’t touch any guano. No, she was not bumped by a bat. Her party entered a short distance and found themselves on a sort of mezzanine, overlooking a lower level, with bats just above and two pythons below. Some of the other tourists left quickly. She and Rick lingered, trying to absorb the scene. “When again are we going to see pythons and bats in a cave?” she said to me, then caught herself, adding with caustic hindsight: “I can assure you, never.”

  After twenty minutes, they had seen enough. And that was it: no mishaps, nothing dramatic. “I definitely didn’t touch a bat or knowingly touch guano.” They hiked back to their vehicle, where the guide spread out a picnic lunch. Before eating, Barnes used some hand sanitizer that she had brought for such moments. By late afternoon they were back at Queen Elizabeth, in time for a sunset of watching the more conventionally appealing
forms of African wildlife. It was Christmas evening, 2007.

  They arrived home on New Year’s Day. Michelle left again quickly for a postholiday visit with her parents in Iowa. So she was already in Sioux City, on January 4, when she woke up feeling like someone had driven a needle into her skull.

  She was achy all over, feverish, and had this fierce, drilling headache. Suspecting that she might have been bitten by an insect, she asked her parents to check her scalp. “Of course, there was nothing. And then, as the day went on, I started developing a rash across my stomach.” The rash spread. Besides the aches and pains, the exhaustion, the rash, she began to feel discombobulated. “Over the next forty-eight hours, I just went down really fast.” She was still on malaria prophylaxis, from the trip, and to that she now added some Cipro and ibuprofen. No relief. But she toughed out the visit, flew back to Colorado, and stopped into an Urgent Care near her home in Golden, where they don’t see a lot of Marburg virus disease. The doctor there took blood for testing, gave her painkillers, and sent her home. The blood sample got lost.

  After that inconclusive consultation, plus two more with her regular doctor in the following two days, Michelle Barnes turned up at a hospital in suburban Denver. She was dehydrated; her white blood count was imperceptible; her kidneys and liver had begun shutting down. Once admitted, she faced a parade of doctors and a litany of questions. Among the first questions was: What have you been doing for the past four days? Most people seek help before multiple organ failure sets in. I’ve been sucking it up, Barnes answered. Her far-flung sisters, one of whom was a doctor in Alaska, converged on the hospital—which was gratifying to Michelle, but also alarming. Clearly, they had been given to understand that she might be going down. The doctor-sister, Melissa, played a key role in pressing Michelle’s physicians for information and action. That’s when an infectious disease specialist, Dr. Norman K. Fujita, joined the team. Fujita arranged for Michelle to be tested for leptospirosis, malaria, schistosomiasis, and other infections that might be contracted in Africa, such as Ebola and Marburg. All came back negative, including the test for Marburg.

  Nobody knew what she had. But they could see her declining. The hospital doctors tried to stabilize her with hydration and antibiotics and oxygen, tried to ease her suffering with pain meds, while hoping her body would pass through the onslaught, whatever it was, and heal. The crisis must have arrived on the night of January 10 or 11, by Michelle’s blurry recollection, when another of her sisters sat with her all night and showed signs of dire concern that Michelle was about to check out. One curious thing about that night, Barnes recalled, was that she’d been placed in a pediatrics ward. There was no room anymore in the ICU. “So, for whatever reason, they transferred me to pediatrics. I know because someone came around and gave me a teddy bear.” Unlike Astrid Joosten in Leiden, unlike Kelly Warfield at USAMRIID, Michelle Barnes was never put into an isolation unit. Sometimes her caregivers wore masks, as a precaution, and often they didn’t. Gradually her body regained strength and her organs (all except her gall bladder, which had been surgically removed) began to recover. The teddy bear may have helped more than the antibiotics.

  After twelve days, she left the hospital, still weak and anemic, still undiagnosed. In March she saw Norman Fujita on a follow-up visit and he had her serum tested again for Marburg. Again, negative. Three more months passed and Michelle, now gray-haired, lacking her old energy, suffering abdominal pain, unable to focus, got an email from a knowing friend—a journalist she and Rick had met during the Uganda trip—who had just seen a news article about which he thought Michelle should know. In the Netherlands, a woman had died of Marburg after a Uganda vacation during which she had visited a cave full of bats.

  Barnes spent the next twenty-four hours googling up every article on the case she could find. By a small-world coincidence, she had lived in the Netherlands for three years herself, during the 1990s, so she could read the coverage in Dutch as well as in English. Early the following Monday morning, she was at Dr. Fujita’s door. “I’m an emergency, I need to speak with you,” she said. Fujita welcomed her in and listened to the new information. Beyond his polite demeanor, she felt, he must be rolling his eyes and thinking, Great, another person who diagnoses herself from the Internet. But he agreed to test her a third time for Marburg. That sample went to the CDC, as had the earlier ones, and again tested negative; but this time a lab technician, aware that the patient had visited a cave inhabited by Marburg-infected bats, cross-checked the third sample, and then the first sample also, using a more sensitive and specific assay. Boing.

  The new results went to Fujita, who called Barnes with some left-handed congratulations: “You’re now an honorary infectious disease doctor. You’ve self-diagnosed, and the Marburg test came back positive.”

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  News of the Joosten case also reverberated at the CDC. Soon afterward, in August 2008, another team was dispatched to Uganda, this time including the veterinary microbiologist Tom Ksiazek, a veteran of field responses against zoonotic outbreaks, as well as Towner and Amman. Bob Swanepoel and Alan Kemp were again mustered from South Africa. “We got the call, ‘Go investigate,’ ” Amman told me. Their mission now was to sample bats at Python Cave, where this Dutch woman (unnamed in the epidemiological traffic) had become infected. Her death, her case history, implied a change in the potential scope of the situation. That local Ugandans were dying of Marburg was a severe and sufficient concern—sufficient to bring a response team in haste from Atlanta and Johannesburg. But if tourists too were involved, tripping in and out of some lovely python-infested Marburg repository, in Tevas and hiking boots, blithe, unprotected, and then boarding their return flights to other continents, the place was not just a peril for Ugandan miners and their families. It was also an international threat.

  The team converged at Entebbe and drove southwest. They walked the same trail that Joosten and Barnes and their husbands had walked, to the same opening amid the forest vegetation. Then, unlike the others, they donned their Tyvek pajamas, their rubber boots, their respirators, and their goggles. This time, with cobras in mind, they added snake chaps. Then they went in. Bats were everywhere overhead; guano was everywhere underfoot. In fact, the rain of guano seemed to come so continuously, Amman told me, that if you left something on the floor it would be covered within days. The pythons were indolent and shy, as well-fed snakes tend to be. One of them, by Amman’s estimate, stretched about twenty feet long. The black forest cobras (yes, more of them here too) kept to the deeper recesses, away from heavy traffic. Towner was gazing at a python when Amman noticed something glittery on the floor.

  At first glance it looked like a bleached vertebra, lying in the excremental glop. Amman picked the thing up.

  It wasn’t a vertebra. It was a string of aluminum beads with a number attached. More specifically, it was one of the beaded collars that he and Towner had placed on captured bats at Kitaka Cave, the other Marburg cave, three months earlier and thirty miles away. The code tag spoke one simple fact: Here was collar K-31, from the thirty-first animal they had released. “And of course, I just lost my mind,” Amman told me. “I was, ‘Yeah!’ and jumping around. Jon and I were so excited.” Amman’s insane jubilance was in fact just the sane, giddy thrill that a scientist feels when two small bits of hard-won data click together and yield an epiphany. Towner got it and shared it. Picture two guys in a dark stone room, wearing headlamps, high-fiving in nitrile gloves.

  Retrieving the collar at Python Cave vindicated, in a stroke, their mark-recapture study. “It confirmed my suspicions that these bats are moving,” Amman said—and moving not only through the forest but from one roosting site to another. Travel of individual bats (such as K-31) between far-flung roosts (such as Kitaka and Python) implied circumstances whereby Marburg virus might ultimately be transmitted all across Africa, from one bat encampment to another. It suggested opportunities for infecting or reinfecting bat populations in sequence, like a string of blinking Christma
s lights. It voided the comforting assumption that this virus is strictly localized. And it highlighted the complementary question: Why don’t outbreaks of Marburg virus disease happen more often?

  Marburg is only one instance to which that question applies. Why not more Hendra? Why not more Nipah? Why not more Ebola? Why not more SARS? If bats are so abundant and diverse and mobile, and zoonotic viruses so common within them, why don’t those viruses spill into humans and take hold more frequently? Is there some mystical umbrella that protects us? Or is it fool’s luck?

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  The ecological dynamics of the virus itself may be part of the reason that such diseases aren’t constantly raining down. Yes, viruses do have ecological dynamics, just as do creatures that are more unambiguously alive. What I mean is: They’re interconnected with other organisms at the scale of landscapes, not just at the scale of individual hosts and cells. A virus has geographical distribution. A virus can go extinct. The abundance, survival, and range of a virus all depend upon other organisms and what those do. That’s viral ecology. In the case of Hendra, to take another instance, the changing ecology of the virus may partly account for its emergence as a cause of human disease.

  This line of thought has been explored by an Australian scientist named Raina Plowright. Trained first as a veterinarian, Plowright worked on domestic animals and wildlife in New South Wales and overseas—Britain, Africa, Antarctica—before fetching up at the University of California, Davis, to do a master’s degree in epidemiology and then a doctorate in the ecology of infectious diseases. She is one of this new breed of cross-trained disease specialists I’ve mentioned, veterinarian-ecologists who recognize the intimate connectedness of human health, wildlife health, livestock health, and the habitats we all share. For her doctoral fieldwork, Plowright returned to Australia to investigate the dynamics of Hendra virus within one of its reservoir hosts: the little red flying fox. She did some of her trapping and sampling in the Northern Territory, south of Darwin, amid the eucalyptus and melaleuca forests in and around Litchfield National Park. That’s where I spoke with her, during one idle morning in 2006, as Cyclone Larry swept across northern Australia, drenching the land and raising the rivers and creeks. We had some time to kill before she went out once again and tried to catch bats amid the monsoonal flooding.