I am no master of venereal diseases, and perhaps I am somewhere mistaken. Despite that, the original basis for my argument was grounded solely around the idea that the disease (lycanthropy) is spread through all forms of body fluids. As with the spread of saliva, blood, sexual fluids, breast milk, mucus, etc. may spread the disease. There are STDs, (e.g. AIDs) that may be spread through some body fluids, and not contact.
Bites transmit lycanthropy. How? Saliva getting into the blood stream. So transmission of bodily fluids between subjects will trasmit lycanthropy.
While this is perhaps not how all people choose to view lycanthrophy, this is again the standard definition with which I subscribe, and am sharing and arguing for.
Since this is fantastical, you can then play around with the rules to be more suitable with the setting as it could get really out-of-control if you have a person being contagious at all times. Drinking from the same well, or bathing in the same water can potentially become a dangerous means for transmitting the disease. If the laws of how lycanthropy is spread is such that the infected persons' saliva is not contagious while not transformed, this alleviates the initial problem. Why this might occur? I am not completely sure, as I have stated, I am no master of venereal diseases. But perhaps this form of infection is, in this way, different from any real life venereal diseases. This is a fantastical infection/curse, and it does not mean that it has to be like any specific diseases, just that it is plausible. Perhaps it is that while in normal form the lycanthrope is not contagious at all.
Again, however, the way that I view lycanthropy is that it should be spread through sexual fluids despite being transformed or not. Perhaps this form of the disease is dangerously contagious while transformed into a were-beast (spreading through saliva), but acts more like AIDs while not transformed.
And I don't think sexual transmission would ever be the primary cause of transmission, unless perhaps it is through someone who is especially promiscuous or is trying to knowingly spread the disease. However, I think that would be a pretty rare case, compared to most cases of lycanthropy. As were-beasts
classically tend to be more violent, attacking peoples, that the bite would be most likely cause of spreading the disease on a regular basis.
Perhaps it is wrong to outrightly classify it as an STD, however it does not change the fact that, by this definition, it happens to be a disease that is sexually transmissible.
I also have not seen any instances where the common cold or rabies are spread by sexual fluids. Do you have any sources on that?