Helper virus

When helper viruses is Virus , the incomplete to complete viruses (called virusoids ) are needed since the latter, the genetic information for important structural components are missing. Virusoids would not be able to multiply without helper viruses.

A classic example is the hepatitis D virus, a virusoid that lacks an important structural component of the shell, the HBsAG (hepatitis B surface antigen). The helper virus in this case is the hepatitis B virus ( HBV ), which provides the missing components. For this reason, hepatitis D infection only occurs together with hepatitis B infection.