Tess Gerritsen - Gravity

Abruptly she opened her eyes and realized that she had been sleeping.

Dreaming. Her shirt was saturated with sweat. It was a good sign. It meant that her fever had eased off.

She massaged her temples, trying to force out the images from her dream, but she could not, reality and nightmares had merged into one.

She stripped off the sweat-soaked shirt and put on a clean one from Diana's locker. Despite the bad dreams, that brief nap had refreshed her, and she was alert again, ready to search for new solutions. She floated into the U.S. Lab and pulled up all the files on the computer.

It was an extraterrestrial organism, Todd Cutler had informed her, and everything NASA now knew about the lifeform had been transmitted to her onboard computers. She reviewed the files, hoping to find some new inspiration, some approach that no one else had thought of. Everything she read was dismally familiar.

She opened the genome file. A nucleotide sequence spilled across the monitor in an unending stream of As, Cs, Ts, and Gs.

Here was Chimera's genetic code -- parts of it, anyway. The parts USAMRIID had chosen to share with NASA. She stared, hypnotized, as the lines of code marched down the screen. This was the essence of the alien lifeform now growing inside her. It was the key to the enemy. If only she knew how to use it.

The key.

She suddenly thought of what Jack had said earlier, about hormones. In order for a hormone to work, it has to bind to a receptor on the target cell. It's like a key in search of just the lock in which to fit.

Why would a mammalian hormone like HCG suppress the reproduction of an alien lifeform? she wondered. Why would an extraterrestrial organism, so foreign to anything on earth, properly fitting locks to our keys?

On the computer, the nucleotide sequence had finished scrolling to the end. She stared at the blinking cursor and of the earth-born species whose DNA had been raided by Chimera.

By acquiring those new genes, this alien lifeform had become part human. Part mouse. Part amphibian.

She got on the comm with Houston. "I need to speak to somebody in Life Sciences," she said.

"Any one in particular?" asked Capcom.

"An amphibian expert."

"Stand by, Watson." Ten minutes later, a Dr. Wang from NASA Life Sciences came on the loop. "You had a question about amphibians?" he asked.

"Yes, about Rana pipiens, the northern leopard frog."

"What can I tell you about it?"

"What happens if you expose the leopard frog to human hormones?"

"Any hormone in particular?"

"Estrogen, for instance. Or HCG." Dr. Wang answered without hesitation.

"Amphibians in general are adversely affected by environmental estrogens. It's been quite a bit, actually. A number of experts think the worldwide decline in frog populations is due to estrogenlike substances polluting streams and ponds."

"What estrogenlike substances?"

"Certain pesticides, for instance, can mimic estrogens. They disrupt the frogs' endocrine systems, making it impossible for them to reproduce or thrive."

"So it doesn't actually kill them."

"No, it just disrupts reproduction."

"Are frogs in particular sensitive to this?"

"Oh, yes. Far more than mammals. Plus, frogs have permeable skin, so they're susceptible to toxins in general. That's sort of their, well, Achilles' heel." Achilles' heel. She fell silent for a moment, thinking about that.

"Dr. Watson?" said Wang. "You have any other questions?"

"Yes. Is there any disease or toxin that would kill a frog, but not harm a mammal?"

"That's an interesting question. When it comes to toxins, it would depend on the dose. You give a little arsenic to a frog, you'd kill it. But arsenic would kill a man as well, if he's given a larger dose. Then again, there are microbial diseases, certain bacteria viruses, that only kill frogs. I'm not a physician, so I'm not absolutely certain they're harmless to humans, but -- "

"Viruses?" she cut in. "Which ones?"

"Well, Ranaviruses, for instance."

"I've never heard of those."

"Only amphibian experts are familiar with them. They're DNA viruses. Part of the Iridovirus family. We think they're the cause of the tadpole edema syndrome. The tadpoles swell up and hemorrhage."

"And that's fatal to them?"

"Very much so."

"Does this virus kill people as well?"

"I don't know. I don't think anyone does. I do know Ranaviruses have killed off whole populations of frogs around the world." The Achilles' heel, she thought. I've found it.

By adding the leopard frog's DNA to its own genome, Chimera had become part amphibian. It had also acquired an amphibian's vulnerabilities .

She said, "Is there any way to obtain live samples of one of these Ranaviruses? To test against Chimera?"

There was a long silence. "I get it," said Dr. Wang. "No one's tried that yet. No one's even considered -- "

"Can you get the virus?" she cut in.

"Yes. I know two amphibian research labs in California who are working with live Ranaviruses."

"Then do it. And get hold of Jack McCallum. He needs to know about this."

"He and Gordon Obie just left for White Sands. I'll reach them there."

Tumbleweeds skittered across the road, swept along in a stinging cloud of sand. The men drove past the guardhouse, past the electrified fence, and into the barren Army compound. Jack and Gordon stepped out of the vehicle and squinted up at the sky. The sky was a dusky orange, obscured by windblown dust. The color of sunset, not high noon. They had managed to catch only a few hours of sleep before they'd taken off from Ellington, and it hurt Jack's eyes just to see the light of day.

"This way, gentlemen," the driver said.

They followed the soldier into the building.

It was a different reception from the last time Jack had visited.

This time the Army escort was polite and respectful. This time Dr. Isaac Roman was waiting at the front desk, although he did not look particularly happy about their arrival.

"Only you are allowed to come with me, Dr. McCallum," he said. "Mr. Obie will have to wait here. That was the agreement.

"I made no such agreement," said Jack.

"Mr. Profitt did, on your behalf. He's the only reason you're being allowed in this building. I haven't a great deal of time, let's get this over with." He turned and walked to the elevators.

"Now, there's your standard Army-issue asshole," said Gordon.

"Go on. I'll wait here."

Jack followed Roman into the elevator.

"First stop is subbasement level two," said Roman, "where we house our animal trials." The elevator door opened, and they confronted a wall of glass. It was a viewing window.

Jack approached the window and stared at the laboratory beyond. Inside were a dozen workers wearing biocontamination suits. Cages held spider monkeys and dogs. Right beside the window were glass-enclosed rat cages.

Roman pointed to the rats.

"You'll notice each cage is labeled with the date and time they were infected. I can think of no better way to illustrate Chimera's nature."

In the Day 1 cage, the six rats appeared healthy, vigorously spinning their exercise wheels.

In the cage labeled "Day 2," the first signs of illness appeared.

Two of the six rats were shivering, their eyes a bright bloodred.

The other four were huddled in a lethargic heap.

"The first two days," said Dr. Roman, "is Chimera's reproductive phase. You understand, this is completely opposite to what we see on earth. Usually a lifeform must reach maturity before it begins to reproduce. Chimera reproduces first, and then begins to mature. It divides at a rapid rate, producing up to a hundred of itself by forty-eight hours. They start out microscopic in size -- not visible to the naked eye. Small enough so that you could breathe them in, or absorb them through your mucous membranes, and not even know you've been exposed."