The Collaborative International Dictionary of English v.0.48:

Viva \Vi"va\, interj. [It.]
   Lit., (long) live; -- an exclamation expressing good will,
   well wishing, etc. -- n. The word viva, or a shout or sound
   made in uttering it.
   [Webster 1913 Suppl.]

         A wilder burst of "vivas".               --R. H. Davis.
   [Webster 1913 Suppl.]