In this novel, vampires are formed from a man made plague which changes humans into vampires.
Step-by-step explanation:
I am legend is one of the most famous novels that has been written by Richard Matheson. In this, Robert Neville who is a brilliant scientist is the only survivor of man made plague which has resulted in the changing of the humans into mutants who are thirsty of blood.
In the story, Neville is seen roaming about in the hope of finding other survivors but he knows that the odds and the time are against him and is not in his favor.