  This paper is the first of a series giving a self-contained way from the
Neveu-Schwarz algebra to a new series of irreducible subfactors. Here we
present an elementary, progressive and self-contained approch to vertex
operator superalgebra. We then build such a structure from the loop algebra
$Lg$ of any simple finite dimensional Lie algebra $g$. The Neveu-Schwarz
algebra $Vir_{1/2}$ emerges naturally on. As application, we obtain a unitary
action of $Vir_{1/2}$ on the unitary discrete series of $Lg$.
