Remy leaned closer as he worked. “Dr. Whitaker, if I may ask, why are you only concentrating on bats for your viral studies?”
Frank sat back as he used a wax pencil to catalog the sample in hand. “Basically because these little fellas are furry sacks of viruses. Not only do they naturally harbor hundreds of species, but they’re also great reservoirs of environmental viruses. They pick up all sorts of arthropod viruses from the insects they eat. Even plant viruses, in fruit-eating bats. In turn, they pass those viruses to other wildlife—or even humans. Ideally, it would be great if we could survey the virosphere of every vertebrate, invertebrate, and plant out there. But that’s not practical, if even possible. So, in the meantime, bats make excellent monitors for what lurks out there in the environment at large.”
“I see,” Remy said. “But I’ve always wondered, with all that exposure to viruses, why don’t bats get sick?”
Frank settled the roundleaf bat to the cave floor and set about untangling another, which from its shape and size was a fruit bat, Rousettus aegyptiacus.
“Three reasons,” Frank answered. “First, bats are superstars when it comes to their unique immune systems. Research suggests they gained this ability because they’re the only mammal that flies.” He unfolded a large wing and poked a vein with a needle and sapped a few drops of blood into a pipette. “To accomplish this miraculous feat requires a metabolism that’s on hyperdrive. All that metabolic heat ramps up their tiny bodies to a feverish state that helps hold back infections.”
Frank set down the pipette and picked up a swab. “The second reason—and a more important one—such a boosted metabolism produces a slew of dangerous inflammatory molecules, which can be deadly. To combat this, in their evolutionary past, bats disabled ten genes. This dampened their inflammatory response and kept their immune system from overreacting—an exaggerated response called a cytokine storm, which causes the most deaths from viruses. In addition, inflammation is a major cause of aging, so dampening this process accounts for why bats live up to forty years, an extraordinary feat for such a small mammal.”
Frank lifted the swab, and Remy helped him pry open the test subject’s tiny jaws, exposing the needle-sharp fangs.
“You said there were three reasons bats are resistant to getting sick,” Remy noted. “What’s the third?”
“Ah, for that answer, you have to look at a bat’s DNA. Most of their code—ours, too, for that matter—contains fragments of ancient viral code, bits of DNA incorporated into their genome from past exposures. Bats wield those genes in unique ways. They can split them off into their cellular cytoplasm and turn those bits into antibody factories.”
“Which keeps them healthy.” Remy gave a sad shake of his head. “If only we could do the same. My team is still trying to stamp out Ebola flare-ups throughout West Africa. As soon as we snuff one out, another springs up.”
Frank nodded grimly. He finished with the fruit bat and searched the spread of the net. It lay limp and empty.
“It appears we’ve run out of volunteers,” Frank said.
“Just as well. It must be close to sunset. We should head back.”
Frank agreed. He had no desire to trek to his campsite in the dark. Working together, they set about clearing their site. Frank packed away the last of his samples, while Remy gathered up the net from the floor. Once finished, they set off, letting their test subjects wake and return to their roosts.
Frank glanced back as the first couple of bats took wobbly flights into the air. “Best we clear out of here before the rest take wing.”
“Why’s that?”
“While bats are great at keeping their viral load in check, if any of them gets too hassled or anxious, that complicated immune system breaks down. Then the viruses proliferate, making the bat all the more infective.” Frank glanced over to Remy. “Always remember: a stressed bat is a dangerous one.”
“I will keep that in mind.”
Remy set a swifter pace away from the collection point and glanced back periodically with a worried expression. They quickly reached the flooded section of the cavern and waded back toward the exit. As they did, Frank kept a wary watch for any of those glowing red eyes in the water, but he spotted none of them. Apparently, the commotion and noise of their labors had driven the crocodiles into the deeper caves.
“What’s next?” Remy asked, nodding to Frank’s backpack. “What do you do now with all those samples?”
“I’ll get them over to my campsite’s mobile lab. I can do a preliminary analysis via PCR amplification, comparing the viral antigen sequences to a genetic database. It will help me catalog known viruses. I’ve also developed a set of reagents and nested primers to identify unknown viruses. It’s crude, but using SISPA—single primer amplification—I can attach linker/adaptors of a known sequence to an unknown sequence, which lets me amplify—”
Remy held up a hand. “I believe you.”
Frank smiled. “Sorry. It’s the best I can manage in the field. The gold standard, of course, would be to grow any of those unknown viruses in a cell culture. But that’s too dangerous outside of a biocontainment unit. Like what you have at your research center in Franceville.”
He envied Remy and his crew at CIRMF. They had both a primatology lab and a biosafety Level 4 containment facility. If I had full use of that facility . . .
Remy must have sensed his desire. “If you find anything particularly intriguing, I’m sure we can accommodate a viral isolation study. Especially for any samples collected from West Africa. Better to know what’s out here before it becomes a problem.”
“It’s why I’m in Africa. That, and seeing how many mosquito bites it takes before a person is driven mad.”
Remy cocked an eyebrow toward him. “That is one mystery you will surely solve, Dr. Whitaker. Especially with all the storms passing through the area.”
“True.” Frank glanced over a shoulder to the dark waters behind him. “If nothing else, maybe all that rain and flooding will eventually wash these poor crocs back into the sunlit world.”
Remy pointed ahead. “Right now, I’ll be happy to get myself out of here.”
7:22 P.M.
After another half hour, Frank spotted a faint brightness in the tunnel ahead, shining across the breadth of black water.
Remy saw it, too. “Dieu merci . . .” he sighed out.
Drawn by the light, they splashed the last of the way to the entrance. Frank gasped with exhaustion and stood under the threshold. A rope ladder scaled up the seven yards to the bright opening above. Next to it, a thin waterfall streamed into the cavern, casting a fine mist.
Frank lifted his face to the sunlight and tugged off his goggles and mask. He took his first breath of air not fouled by ammonia. Still, the heat stifled. Even this close to sunset, the day had grown only hotter. He swore the humidity had to be a hundred and ten percent.
Remy led the way up the ladder. Frank followed, balancing his heavy pack across his shoulders as he climbed the swaying ladder. At the top, Remy helped him crawl out of the ferny grotto.
With a groan, Frank stood and faced his next challenge. A trampled path led off through dense jungle. The two of them still had a two-mile hike to reach Frank’s makeshift camp. He hoped they could get there before the sun fully set. It already sat low on the horizon.
After drinking deeply from their water bottles, they set off down the path. Both were too tired to do any talking. Within a quarter mile, Frank was sweating through his coveralls. He considered stripping them off, but the effort seemed too taxing. Plus, the suit protected most of his body from the clouds of mosquitoes harassing them.
Where are all those bats when you need them?
Remy suddenly stopped ahead of him.
Frank nearly stumbled into his back. “What’s wrong?”