The Hyde Effect, by Steve Vance. First published in 1986, which fits neatly with your idea that it had been released not long before you happened to read a copy.
Here are some plot points I remember. Some of them strongly resemble your summary-from-memory, although there are some discrepancies. (Not surprising if it's been about 35 years since you read it.)
The book begins much as you described. An anthropologist is listening to members of a primitive tribe talk about how a werewolf had been killing people, twelve years ago, in sprees which always occurred during a full moon, until the tribal shaman was able to come up with a way to kill the monster. The scholar is interested in letting them talk, but personally suspects the "werewolf" was something like a victim of rabies who foamed at the mouth and seemed inhumanly strong as he went on a rampage -- although it is odd that he would survive long enough to launch three killing sprees at monthly intervals. The scholar silently speculates that perhaps there were multiple rabid attackers, in a monthly cycle -- each new one having been infected by the previous before he died of his disease, and only the last of them was somehow trapped and killed by the men of the tribe, who then blamed this "monster" for all of the previous killings.
The scholar is trying to be polite, but evidently his skepticism shows through. The shaman is offended at being patronized by a white man who thinks he already knows all the answers. The shaman had kept a souvenir of the werewolf, dried out and in powdered form, believing it still contained the power to create another werewolf if need be. The shaman (called "Ugalde") puts that special powder into a bottle of whiskey and then . . .
With the swiftness of a man half his age, the Indian leaped from a
sitting position onto the other's chest, as if he were pinning him in
some friendly athletic contest. But the crazed expression covering his
face and the keenness of the knife blade removed any trace of ordinary
competition from the action. Ugalde sat the bottle viciously on the
ground next to the visitor's face and tipped the neck of it toward his
mouth. "Drink," he ordered.
"Ugalde!" the man cried frantically. Visions of wriggling microbes
being revitalized by the liquor flooded his mind. Could any life
survive for a dozen years in such a dehydrated state? Yes, yes,
viruses could live for centuries! "What in the name of God are you
A sneer replaced the sullen look the older man had worn. "Your god!
You believe your eye, white man, and only that, so drink and see what
the devils you don't know can cause a living spirit to become! Drink,
or I will cut your throat!"
Then a good chunk of the book deals with brutal murders taking place, always on the night of a full moon, and various characters getting interested in the investigation, for various reasons. At first, there's a serious lack of surviving eyewitnesses to describe the mysterious attacker to the cops, but gradually the evidence accumulates that something strongly resembling a Hollywood-style werewolf is involved in these homicides. We readers, of course, have a very good idea of how that happened.
Then another large chunk of the book deals with what happens in one horrible night after the anthropologist has been taken into custody. (I think he finally surrendered himself to the police, voluntarily, and described everything he could remember about the incident with the shaman, and what's happened since then on the nights with full moons in the sky.) You are correct that becoming a werewolf appeared to be a type of communicable disease, although I can't recall if it was specifically established, during the novel, to be a "germ" or "virus" or what. You are also correct that silver was particularly effective against a werewolf. Other weapons could pierce its flesh, but it appeared to recover very rapidly from such wounds. (Sort of like Wolverine's mutant "healing factor" in the X-Men comics and movies.)
Much of this later portion of the book, however, takes place during one terrible night. Someone takes the anthropogist's confession seriously enough that he arranges for the next anticipated transformation (on the night of the next full moon) to take place under carefully controlled conditions inside some sort of large scientific research center with lots of armored doors. Video cameras will be rolling. The man will be strapped onto a stretcher, and I believe will be isolated in a room with something resembling steel bars or bulletproof glass or some other way to "keep him locked up," while scientists and journalists in the next room are watching intently to see just what happens. The anthropologist expresses some doubts about whether the leather straps, a couple of inches thick, will be strong enough to keep him helpless on the stretcher after he turns into a werewolf, but of course the chief scientist on this project pooh-poohs the idea that there could be any problems in that area. (You see what's coming, of course.)
Yes, the test subject breaks loose, now transformed into a bipedal werewolf with vastly superhuman strength and stamina, but nothing resembling "moral restraint" or "conversational skills," and goes on a berserk rampage throughout the facility. Various characters try various ways to hide from it, injure it with silver, or otherwise hold it off, and in the end someone manages to kill the monster.
I don't think your memory is accurate about the "sole remaining victim," however. Although it is true that just one of the major characters of the book becomes an infected victim after that night of terror -- but so do many other people whom we readers never really got to know. In the last pages of the book, it is made clear that someone important within the federal government of the USA has finally started taking this situation Very Seriously -- the high death toll and the video evidence of a terrifying transformation probably helped with that -- and so Uncle Sam is now willing to spend huge amounts of money to keep the werewolf virus (or whatever it is) from spreading. After the anthropologist/werewolf was killed, every survivor of that terrible night at the research facility was taken into federal custody, to be detained until the next night of a full moon. Some survivors had been severely wounded; some had scratches and bruises and so forth; some appeared to be unharmed. But no one knew how to do a blood test (or any other lab test of body fluids, tissue samples, etc.) that would absolutely guarantee that a person had not been infected by a drop of saliva or some other fleeting contact with the werewolf, so the only safe thing to do was to make sure that each possible candidate for infection was very securely strapped down, inside rooms which were guaranteed to withstand three times the amount of physical strength that the first werewolf had demonstrated, by the next time the sun set on the night of a full moon.
I forget the exact numbers, but I think over a hundred survivors were being tested this way in a maximum-security facility, and I think around thirty of them did, in fact, transform into raving monsters when the time came. But proper care had been taken so that none of them broke out. The next morning, everyone who had transformed during the night went right back to normal -- for another month. All the other detainees, now confirmed to be uninfected, were quickly turned loose since they were not huge threats to national security. What, exactly, would happen to the "new generation" of werewolves who remained in federal custody? That was left up in the air!
Note: a little research tells me that a Kindle edition of the book is available through Amazon for $3.99 (USD), and also that Vance later wrote a sequel novel -- Shapes -- which I haven't read.