RNA Viruses
- Attachment to host cell receptor.
- Fusion with membrane of host.
- Nucleocapsid enters the cytoplasm.
- Transcription in cytoplasm by viral RNA polymerase.
- Translation by host cell ribosomes.
- Assembly of viral particles.
- Release from cell.
VIRUSES AND INFECTIOUS DISEASE
Viruses are classified by the type of nucleic acid they contain, chemical and
physical properties, shape, structure, host range, and how they replicate.
DNA viruses
DNA viruses are viruses that have DNA but no RNA. Common DNA viruses are:
- Hepadnaviruses. Hepadnavirusescause serum hepatitis. The hepatitis B
virus (HBV) is a common form of this virus that enters the body via hypo-
dermic needles, blood transfusion, or sexual relations. (Hepatitis A, C, D,
E, F, and G are not related and are RNA viruses). - Herpesviridae. Herpesviridaecauses the herpes virus. There are about 100
forms of herpes viruses including:- Herpes simplex virus type I (HSV-1). Herpes simplex virus type I causes
encephalitis and enters the body through lesions on the lip, skin, or eyes. - Herpes simplex virus type 2 (HSV-2). Herpes simplex virus type 2 is
sexually transmitted, affects the genital and lip area, and can lead to
carcinomas.
•Varicella-Zoster Virus (V2V). Varicella-Zoster virus causes chicken-
pox in the acute form and shingles in the latent form. Shingles appears
as vesicles along a nerve resulting in severe pain along the course of
the nerve. - Cytomegalovirus (CMV). Cytomegalovirus causes an infection that usu-
ally goes unnoticed unless the person’s immune system is compromised,
- Herpes simplex virus type I (HSV-1). Herpes simplex virus type I causes
CHAPTER 12 Viruses, Viroids, and Prions^189