The only human disease known to be caused by a viroid is hepatitis D. This disease was previously ascribed to a defective virus called the delta agent. However, it now is known that the delta agent is a viroid enclosed in a hepatitis B virus capsid.

Do viroids cause infection?

They replicate autonomously and move systemically in host plants with the aid of the host machinery. In addition to symptomatic infections, viroids also cause latent infections where there is no visual evidence of infection in the host; however, transfer to a susceptible host can result in devastating disease.

Can viroids infect bacteria?

Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating.