Good beaver, bad beaver
Beaver fever. It sounds like it could be fun. Instinctively, I would place the term nearer to "spring fever" than "cabin fever" on the fun-scale. To me, it rings of tasteless euphemism. To hedge a bet, I'd say beaver fever is suffered by heterosexual men after a cold North American winter---a notorious period of olfactory deprivation during which all the little female sex pheromones freeze en route. Those hot little ice crystals fall to the ground before managing to be inhaled, all winter long, so you can imagine what might happen when things warm up a little. In short, I'd say that cabin fever leads to spring fever which can, left unchecked, lead to beaver fever. But, I would be way off.
I'm not completely wrong, though. Beaver fever, also known as giardiasis, does have something to do with reproduction and the cycle of life, but it's not sexy. Well, not for the organism's host, being me. Apparently, I should not brush my teeth with tap water in Central America, or eat street-side barbecue mystery meat. No matter, I must play host to my unwanted guests, who, I'm told will hang around for about six weeks before I eventually kill them. Until then, I'm sure those little bacteria bastards will have a grand time in my small intestine. It sure feels like they are.
Luckily, my beaver fever has granted me only the more benign of the symptoms, including loss of appetite, stomach cramps and rapid weight loss. Two-and-half kilograms (5 lbs) of recently acquired pudge, shed effortlessly in one week? Hmm. I've had worse guests than that.