Disclaimer: Property of BBC; no money is made from this story.
Exhaustion
The Doctor, to his delight, had been asked to join the judging panel for a recreational mathematics championship. This presented Jack with an ideal opportunity to wander around the artificial moon of Hanfoi and have fun on his own, but all he wanted to do was sleep. It took every ounce of his energy to drag himself to his bedroom in the TARDIS. He barely got his shoes off before falling asleep.
***
When he woke some undetermined length of time later, he felt like he hadn't slept at all. Clearly something was wrong, but Jack was too busy being generally miserable to wonder much about the specifics of his ailment. Besides being exhausted, he was achy all over, the sheets were damp with his sweat, and his stomach protested movement with violent lurches.
He'd missed traveling during his long stay on Earth, but he had liked that he hardly ever got sick. Traveling exposed him to all kinds of nasty ailments. Not for the first time, Jack envied the Doctor's immune system.
He stumbled into the bathroom for a glass of water, and there discovered that he looked like crap. His pale, pathetic reflection stared back at him miserably while he drank. At least his stomach accepted the water without throwing up.
"Aspirin?" he croaked. When he opened the medicine cabinet, the TARDIS had obligingly provided a bottle. Jack took two and decided he'd feel more human after a shower.
The shower helped a little, but left him once again drained. He more or less fell back into bed, noting that the TARDIS had changed his sheets before going back to sleep.
***
He only woke up because there was an insistent Time Lord sitting next to his bed. "Jack, wake up."
Cracking one eye open, he took stock of the situation. He felt pretty much the same as the last time he'd woken up. Sitting took an absurd amount of effort.
"You need liquid." With that, the Doctor handed him a cup of tea. Always with the tea. "You've got the Kantaran Sleeping Flu."
"Just kill me and get it over with." The tea didn't hold much appeal, but under the Doctor's watchful gaze he sipped it anyway.
"You'd revive before the virus was dead, so it wouldn't do you any good. Not that I would in the first place."
It had been worth a shot.
"The Sleeping Flu was designed as a weapon." The Doctor's disapproval came through loud and clear, both in his tone of voice and facial expression. "We must've been exposed to it on Eg'lin, since it was only used in the two hundredth century. Doesn't affect Time Lords."
"Of course," muttered Jack between sips of tea that he wished were coffee.
"The Sleeping Flu virus enabled the Kantarans to build their third empire." Why the Doctor thought he cared about the history of his illness, Jack couldn't imagine. "Until the people of Kantara figured out what their leaders were up to and revolted. Thought it was an empire built on peaceful cooperation, although that really contradicts the whole idea of an empire. Kantarans are immune, so they could release the virus and conquer planets at their leisure."
He had a far more pressing question. "How long will this last?"
"Welllll, you're the first human to come down with it, so…"
"You have no idea," finished Jack, "and I get to be a guinea pig again."
"I have an educated guess: four days to three weeks."
"Three weeks?" If that was the case, it was just as well he'd sleep most of the time; otherwise he might lose his mind.
"It could be worse. Unlagiaroix women need two years to recover, and those are Unlagiaroix years, of course."
That would be worse, since Unlagiaroix years were over two and a half Earth years, but somehow failed to improve Jack's mood much. He'd only sat up and drank half a cup of tea, but felt as though he'd been running for hours. "How long since the math championship?"
The answer was automatic, as Time Lords didn't need watches. "It finished three hours ago, but you've been here seventeen hours."
Jack's eyelids refused to remain open, so he handed his cup to the Doctor. Mid-yawn, he slid back down under the covers and was asleep in seconds.
***
The TARDIS must've alerted the Doctor that he woke up, because when Jack stumbled out of the bathroom he found the Doctor coming in with toast and more tea. Honestly, the way he used tea as a cure-all, you'd think the Doctor actually was English.
Jack sat on his bed and, since his stomach wasn't in open revolt, bit into a piece of toast. "Sorry to be so boring."
"Oh, I'm taking the opportunity to teach myself Kantaran. It's an interesting language."
Lacking an intelligent response, he just took another bite of toast and considered that the Doctor only stepped foot in his bedroom when he was sick. If his brain wasn't muddled, he might've gone further with the thought.
"And I've been tinkering with the secondary interface control. Fixed the multispatial navigation array so it'll be faster, too."
Jack swallowed a mouthful of tea. "It's really not fair that you're immune to just about everything."
"Arguing with biology gets you nowhere, Jack."
"In case you've forgotten, I can't die. Biologically, that shouldn't even be possible."
The Doctor muttered something; Jack didn't catch every word, but was pretty sure he heard the phrases 'isolated event' and 'outside normal parameters.'
He'd taken the aspirin out of the bathroom and now downed another two with his tea. The Doctor gave him a look imbued with just a hint of Time Lord superiority. "That's not going to help."
"It can't hurt. Why the hell are you bringing herbal tea? At least get something with caffeine."
"Artificial stimulation isn't going to help either, and it actually could hurt. The Kantaran Sleeping Flu was designed to neutralize any threat…"
Jack drifted off to the Doctor's oddly relaxing monologue.