As Brandy and Laurie continued to fuck each other's brains out, there was a change going on around them. Considering how many people have been infected in the gym that day and all the sex that had gone on, there was still a lot of highly-infectious girl cum all over the gym that Brandy had never got around to cleaning up. And now that the owner of the gym had also been converted, the tipping point had finally been reached and the lesbian plague reached critical mass. And since there was no other people left to change, the plague started infecting the building itself.
The pussy juices around the gym bubbled before spreading across every surface, causing it to change. A large part of it was mostly color change, with bright pink being the most common color. Carpeting and wallpaper were shifting to more feminine tones. The equipment itself didn't change a lot, though they seemed newer and cleaner. But it was clear that the equipment were more geared towards women than men. The heavier weights shrank down to something women would be more comfortable with lifting. A few of the smaller weights turned into dildos and sex toys that were stored away in corners.
The biggest change was to the men's locker room, a redundant feature in what was quickly become a women's fitness club. But instead of becoming a second women's locker room or disappearing completely, it gained a new purpose. The lockers in it shrank down to smaller sizes as a pit opened up in the middle of the floor. The pit widened and deepened until it became a swimming pool. Water quickly filled it as pink lights lit up along it. The showers sank into the floors and widened out, the shower heads becoming simple holes that sprayed out water as more such holes appeared. Now there were three hot tubs, with aromatherapy soaps and bubbles in nooks.
When the shifting had finished, the unisex gym was now a very feminine women's fitness club, complete with an indoor pool and hot tubs. But of course, the lesbian plague has permeated the structure of the building itself and everything in it. Anyone walking inside would become gradually exposed to the plague, the extension of the infection depending on how much of the equipment they used. Some would be more susceptible to conversion than others. Women were particularly vulnerable to becoming sexy lesbians here. Men might take longer to be changed, but there would surely be enough existing lesbians to speed things along.
Brandy stopped sucking Laurie's nipples to look around the changed office. "Does something seem different to you?" she asked.
Laurie looked around and said, "OMG, the gym got a totally awesome makeover."
"That's nice," said Brandy, "Wanna keep fucking?"
"Gotta better idea," said Laurie as she pulled off her tank top to let her big titties bounce, "How about we do it in the pool?"
"We got a pool now?" asked Brandy, her eyes currently locked on Laurie's big rack.
"Sure and nobody else is gonna be here for hours," said Laurie.
"I like the way you think," said Brandy. The two women quickly headed to the new pool, removing their clothes as they went. With the fitness club closed for the night, they could have as much fun as they wanted. But they were also looking forward to the next day when new people will be coming and catching the plague.