The Chronivac can only make changes to things around and impacting Jeff given this package, direct modification being off limits, so it did the next best thing. When Adam was brought in to infect Jeff, Adam was temporarily modified to have the best possible mutation of lycanthropy to infect Jeff, get past his immune system rapidly, getting straight to work changing him within the next two full moon cycles. Now that Jeff is infected it's part of him and off limits for additional modification, not that it needed any more help.
The added efficiency has its costs, Jeff forgot the last hour of last night because he did get too hot, the memory was baked from his brain before it could make it to long term storage but outside that he was okay. (This mechanism is one reason not everyone survives becoming a werewolf, however losing the activities of the last hour of the night are minimal compared to the universe this disease came from. Common side effects include lower reasoning capability, loss of inhibition, cumulatively: becoming more feral if you will, and often complete personality change, assuming survival)
The infection finally found the self-destruct mechanism for Jeff's immune cells, which began destroying anything that doesn't recognize his modified wolf proteins and ramped up production of new immune cells that will protect Jeff from the subset of things that can attack humans and canines. Thus, Jeff did not die of an auto-immune reaction and the fever broke within minutes as the immune system stopped being able to fight the changes.
So began the work of rebuilding. As more and more of Jeff's cells converted to protein structures that could handle higher temperature without curdling, his body temperature slowly rose once again reaching 102, but this time, as his new normal, not a fever. Now that existing wouldn't kill the host, its time to prepare him for his monthly cycle. All across his body his hair roots began to grow a little bigger, to match that of a wolf, then much bigger to handle building inches of guard hairs in seconds. This forced oil out of pores, reducing some of the acne he was dealing with.
His muscle, tendon and skin structure began to change, more able to stretch without breaking, which is good for the host's survival and ultimately spreading the infection. All across Jeff's skin, new hair follicles began to develop at such density, granting him the ability to produce fur.
Jeff's scrotum relaxed, the 102 degree average body temperature was bad for sperm creation. He was still creating human sperm... just, infected human sperm. His formerly low body temperature had kept his scrotum pressed against his body much of the time leaving Jeff feeling he was underdeveloped which wasn't the case, but trying to go from his now 102 degrees down to 93 degrees required some distance and his balls now hang low.
Lycanthropy targets adults, the demands the disease puts on children's bodies failed to propagate the disease therefore evolutionary pressure leaves the disease dormant until at least mid to late puberty. This allows for the monthly transformation to make new carriers, as well as dormant infection of the host's progeny for future opportunities. If lucky, from the disease's standpoint, infection of the mate will occur. Since the disease is acting like an STD, this variant has best succeeded at spreading when certain characteristics of the host have been enhanced.
Throughout this time Jeff's cardiovascular system was being rebuilt... After all, who would be scared of a werewolf that passes out from low blood pressure mid transformation? Capillaries dilated and further expanded flooding everything inside him out to his skin and hair with the nutrients it needed. But the transformation doesn't just need more blood to occur, it needs to not snap every blood vessel and artery in his body as he suddenly grows significantly in every direction. Therefore, once his heart itself was stronger and more voluminous, his cardiovascular system began growing slack.
His bones began to modify, harvesting existing calcium to grow special segments that, when activated, change shape creating something similar to a lattice, which can then be filled in creating a normal bone and is reversible. This mechanism will soon be much faster than normal bone growth due to creating an array of cells that store extra calcium and potassium and can rush it where needed allowing near instantaneous (comparatively) bone growth.
The most pivotal part of the disease's success is in modifying the host's nutrient uptake, humans have one diet, wolves have another, and werewolves need more than both combined! The initial and regular transformations are calorically expensive and new enzymes appeared in Jeff's stomach shredding food to it's component parts. His stomach and intestinal lining began growing thicker to protect itself.
In his intestines more changes occurred, his microbiome was harvested for their digestion capability and soon his intestinal walls and stomach were creating micro-digesters, organelles that could survive the stomach acid and existing enzymes, and were deployed to destroy specific cells with shocking efficiency and hold onto nutrients to pass to the intestine speeding up digestion and it's efficiency immensely.
Jeff awoke the next morning unaware how drastically his body had changed and was still changing, he looked the same, perhaps the slightest bit flushed due to increased bloodflow to his skin.