There are two classes of human immortals. Supernatural and Natural. The natural immortals are a product of genetic perfection in the same way someone can gain a genetic defect by pure chance. This is evolution’s first hint at our future immortality and ascension to Godhood as a species. The natural immortals claim to fame is simply their longevity and amazing ability to heal. They have no special paranormal powers. On the other hand we have various supernatural immortals. Many of which are derived from magic. Their supernatural abilities can vary greatly. Generally it is impossible for these superhuman’s to catch any type of disease. That includes transformative paranormal ones such as the viruses of vampirism, lycanthropy, and zombification.
Keanu Reeves is the most famous of the natural immortals. Such immortals can get sick but are known to fight off all manner of disease with a vengeance! They usually acquire immunity afterward. For instance Reeves successfully fought off the zombie virus and now being bitten by a Walking Dead is no big deal for him! However that is the weakest of the three aforementioned supernatural viruses. Ancient anecdotal evidence indicates that a natural immortal has a 50% chance of living through the werewolf virus and becoming immune to its ferocious effects. If they can’t beat it they end up dying without ever becoming a werewolf.
The vampire virus is the most powerful and can’t be fought off by a natural immortal. Instead the immortal human body cleverly integrates it into its DNA and grants the subject all vampire powers. In this case it’s a blessing because they completely lack the blood lust or need for blood to thrive and survive. In addition they don’t gain the various vampire weaknesses that include the inability to bask in sunlight without turning to flaming ash! They simply go onward as a supernatural immortal! An immortal that is keenly aware of vampire presence and therefore would make an exemplary Vampire Slayer! This is the reason vampires have never attempted to bring Keanu Reeves across into the dark shadows. Instead they only lust for his scrumptious immortal blood. Thankfully his vampire slaying skills are beyond totally excellent so he keeps the blood suckers at bay!