Is the v5 vampire virus real?
No. No more than the Easter Bunny or the Tooth Fairy.
It appears that the V5 myth rose out of the British TV miniseries Ultraviolet in which the the word "vampire" is never uttered. The government backed vampire hunting squad the main character discovers subtitutes "Code 5" or the Roman numeral V to denote cases and targets. Hence, V5.
A number of vampire enthusiasts who have taken role playing and fantasy a bit too far, latched on to the misattribution, and adopted it as the rationalization of bizarre, unstable behavior.
More recently, the V5 myth has transformed slightly, and become the K-17 Virus myth. Rather than transliterate from the film, vampire fans stole the idea directly from the 2002 movie Reign in Darkness. Vampire apocalypse movies such as these seem to bring dysfunction out of the woodwork.
No. Vampires are not real. The Vampire Virus (V5) is just a myth. Since there are no vampires and no vampire virus; no one can get infected and die from it. As for fictional stories which contain vampires: it is entirely up to the author whether someone can die in a fictional world. Most vampire stories contain different rules for how vampirism works. But fiction is not reality.
In the real world, it's not possible because vampires like in the movies do not exist. However the most popular answer is that a vampire must first drink or drain much of the human blood out of their victim. Then the victim has to drink some of the vampire's blood. This is the only way to get the vampire virus into a humans system. It then spreads throughout their body turning them into a vampire.