Infectious organic structures that require a host cell to multiply, as they themselves have no metabolism. Enveloped viruses (e.g. vaccinia virus, HBV or HIV) have a viral envelope until replication and are comparatively easy to inactivate (required spectrum of efficacy: limited spectrum of virucidal activity). Non-enveloped viruses (e.g. Polio, hepatitis A virus), on the other hand, are more resistant to disinfectants (required spectrum of efficacy: virucidal).