Generally, tumor viruses cause little or no disease after infection in their hosts, or cause non-neoplastic diseases such as acute hepatitis for hepatitis B virus or mononucleosis for Epstein–Barr virus.
Xeralmente, os virus tumorais causan poucas ou ningunha enfermidade cando infectan aos seus hóspedes, ou causan doenzas non neoplásicas como a hepatite causada polo virus da hepatite B ou a mononucleose causada polo virus de Epstein-Barr.