Summary of DNA & RNA viruses of medical imporatnce

1. M.A.A.Al-Maqrashi
virus N. A Morphology Characteristics & special features Clinical Features
[Adenoviruses]
Linear
Ds.
DNA
- Non-enveloped
- Icosahedral
- Larger and more
complex than
papovaviruses = 70
nm
- Assemply in nucleus
- Released by cell lysis
- Code for their own dna polymerase + dna packaging
proteins
- Host cell provide:
- DNA synthesis accessory factors
- RNA synthesis and modification enzymes
- Early genes: scattered  functional proteins.
- Late genes: in block  structural proteins.
- URT infections
- GIT infections
- Conjunctivitis
- Cystitis
- Tumors in animals
[Herpesviruses]
Herpes simplex
virus [HSV]
Ds.
DNA
- Enveloped
- Icosahedral
- Larger and more
complex than
adenoviruses
- Latency:
Site: trigeminal, cranial, cervical or sacral ganglia
How?
During primary infection, the virus travel via sensory nerves
from the site of infection to sensory ganglion, can stay in
viable state until reactivation.
Activity: producing one mRNA: latency transcript
Reactivation by UV light, heat, fever, stress, …
- Neonates: fatal
- older children & adult: minor
Ep. Lesion:
HSV-1: facial-oral
HSV-2: genital tract
- Rare: fatal HSV encephalitis
Epstein Barr virus
[EBV]
- Latency:
Site: B-cells
Activity: production of protein required for maintaining the
genome within the cell [no viral replication]
Reactivation occurs during immune-suppression
- infants: mild febrile illness
- Teens: Infectious mononucleosis
[glandular fever]
- contribute to:
Burkitt’s lymphoma [Africa]
Nasopharyngeal carcinoma
[China]
Varicella zoster
virus
[VSV]
- Latency:
Site: dorsal root ganglia
Reactivation as zoster is usually limited to one dermatome,
most common:
- Thoracic region
- Area supplied by V1
- primary infection [varicella /
chickenpox] → generalized
- reactivated infection [zoster or
shingles] → localized to one/few
dermatomes
Cytomegalovirus
[CMV]
- Latency:
Site: BM progenitor cells of myeloid
Activity: viral RNA transcripts of early genes
- widespread infection: Most adults have antibody to virus
- Congenital disease is more difficult than rubella:
- Healthy individuals: mild febrile
illness
- Immunocompromised
individuals: Fatal pneumonia

2. M.A.A.Al-Maqrashi
maternal infection is symptomless, and the fetus can be
damaged in any of the three trimesters of pregnancy.
[CMV is major problem for
transplant pts]
[Hepadnaviruses]
Hepatitis B virus
[HBV]
Ds.
DNA
- Enveloped
- Icosahedral
- Carrier/presistant state:
Acute hepatitis B:
90%: complete recovery
1%: Death
5-10%: chronic hepatitis → cirrhosis → hepatocellular carcinoma
[Picornaviruses]
+Ss.
RNA
- Non-enveloped
- Icosahedral
- Small
- One of the largest families of viruses [≈ 230 members]
Enteroviruses [Polioviruses, Coxsackieviruses, Echoviruses]
111 serotypes
Hepatoviruses [Hepatitis A] 2 serotypes
Rhinoviruses [common cold] 105 serotypes
80% of Polio and enteroviruses:
- Replicate in GIT
- Shed in faeces
- Inapparent infection
- long life immunity
[Togaviruses]
Rubella virus
+Ss.
RNA
- Enveloped
- Icosahedral
[Flaviviruses]
+Ss.
RNA
- Enveloped
- Icosahedral
- Yellow fever
- Dengue
[Rhabdovirus]
vesicular stomatitis
virus [VSV]
rabies virus
Non-Sg
- Ss.
RNA
- Enveloped
- Bullet-shaped
Steps of infection:
1. Virus enters via animal bite
2. Virus replicates in muscle at site of bite
3. Infects PNS and ascent via sensory nerves to dorsal root ganglion where it replicates.
4. ascent rapidly in spinal cord to infect CNS
5. Descent via nerves to other tissue [e.g. eye, skin, salivary glands…]
[Reoviruses]
Rotavirus
Colorado tick fever
virus
Sg
Ds.
RNA
- Non-enveloped
- Icosahedral
- triple-layered
[Paramyxoviruses]
Parainfluenza virus
Mumps virus
Measles virus
Respiratory syncytial
virus [RSV]
- Ss.
RNA
- Enveloped
- Icosahedral
RSV: local infection
Children [<12months]: Sever respiratory distress
Infection causes
- necrosis of the bronchiolar epithelium
- Slough-obstruction with mucus
- Leads to alveoli collapse
Measles: systemic infection
- virus replicates in the lymph nodes
- Through the blood, virus goes to the RT

3. M.A.A.Al-Maqrashi
- Giant cells are formed
- Measles only rarely has side-effects in healthy well-nourished children.