The Collaborative International Dictionary of English v.0.48:

HS2 \HS2\, HSV-2 \HSV-2\, HSV-II \HSV-II\n.
   1. Herpes simplex 2, a herpes virus that can cause genital
      herpes; also called type II Herpes.

   Syn: herpes simplex 2.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

HS2
    n 1: a herpes virus that can cause genital herpes [syn: herpes
         simplex 2, HS2, HSV-2, HSV-II]