DNA Viruses

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Created by
Aya Viyar

Cards (140)

  • Poxviridae

    • Poxviruses exist everywhere and may cause diseases in both humans and animals
    • Brick or oval-shaped viruses with large double-stranded DNA genome
    • Infection in humans usually follows contact with contaminated animals, people, or materials, resulting in lesions, skin nodules, or rashes
    • Some poxviruses like smallpox no longer exist in nature, but others like monkeypox virus, orf virus, molluscum contagiosum, and others can still cause diseases
  • Molluscum contagiosum virus

    • Infection caused by the Molluscum contagiosum virus resulting in a benign, mild skin disease characterized by lesions that can appear anywhere on the body
    • Lesions are small raised, white, pink, or flesh-colored with a dimple in the center, ranging from the size of a pinhead to as large as a pencil, can be itchy, sore, red, and swollen
  • Replication of Molluscum contagiosum virus
    Fusion with host membrane, becoming double-walled, rely on host enzymes for replication
  • Transmission of Molluscum contagiosum virus

    Spreads from direct person-to-person physical contact and through contaminated fomites, can spread through autoinoculation, sexual contact, lives on the top layer of the skin
  • Virus transmission

    1. Someone can spread the virus to other parts of his body by touching or scratching a lesion and then touching the body somewhere else (autoinoculation)
    2. Molluscum can spread from one person to another by sexual contact
    3. Once the lesions are gone, the virus is gone as well and there will be no more transmission. MCV is unlike herpes viruses that can remain dormant for long periods and then reappear
  • People with weakened immune systems (i.e., due to HIV, cancer) are at higher risk for getting molluscum contagiosum
  • Atopic dermatitis may be a risk factor due to breaks in the skin
  • People who live in warm and humid climates, and in crowded areas, may also be at risk
  • Characteristics of Mollusca lesions

    • Small, raised, usually white, pink, or flesh-colored with a dimple or pit in the center
  • Treatment

    1. In mild cases in healthy individuals, treatment may be unnecessary. However, any underlying atopic diseases, and the desire to prevent transmission, may need immediate therapy
    2. Physical removal of lesions may include cryotherapy, curettage, and laser therapy
    3. Oral cimetidine is an alternative treatment for small children who are scared of physical removal
    4. Podophyllotoxin cream (0.5%) is a reliable home therapy for men but is not advised for pregnant women due to possible toxicity to the fetus
    5. Other options for topical therapy include iodine, salicylic acid, potassium hydroxide, tretinoin, and cantharidin
    6. Most therapies are effective in immunocompetent patients, but not for those with immunosuppressing conditions such as HIV and cancer
  • Severe case of molluscum on an immunocompromised patient’s back
  • Prevention

    1. Wash hands
    2. Keep molluscum lesions covered
    3. Do not share towels, clothing, or other personal items
    4. People with molluscum should avoid contact sports unless all lesions are securely covered
    5. Do not scratch or pick at molluscum lesions
  • Herpesviridae viral structure

    • Core contains a large, double-stranded DNA genome, Capsid is an icosahedral protein shell, Tegument is a non-membrane-bound layer, Envelope is a lipid bilayer membrane
  • Subfamilies of Herpesviridae

    • Alphaherpesvirinae
    • Betaherpesvirinae
    • Gammaherpesvirinae
  • Alphaherpesvirinae characteristics

    • Short-lived, acute infections with rapid replication, Ectodermal tissue tropism, Latency in sensory neurons
  • Betaherpesvirinae characteristics

    • Wider range of infection types, including lytic and latent phases, Grow slowly, Latency in salivary glands, kidneys, lymphocytes
  • Gammaherpesvirinae characteristics

    • Lifelong latent infections, reactivating under specific conditions, Malignant catarrhal fever virus, Latency in lymphoid cells
  • Herpesviridae characteristics

    • Core with a large double-stranded DNA genome, enclosed by an icosahedral capsid made of capsomers, Capsid is enveloped in a tegument
  • Viruses

    • Malignant catarrhal fever virus
    • Lymphoproliferative diseases
  • Viruses exhibit latency, where the virus can remain dormant in host cells and reactivate later
  • Viruses

    • Have a core with a large double-stranded DNA genome, enclosed by an icosahedral capsid made of capsomers
    • The capsid is enveloped in a tegument, surrounded by a lipid bilayer envelope bearing glycoproteins
    • Classified into 3 subfamilies: Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae
    • Replication and transcription happen inside the nucleus, while translation happens outside the nucleus (in the ribosomes)
  • Physiology of Herpesviruses

    1. Latency and Reactivation: Herpesviruses remain dormant, reactivating under stress or immune suppression
    2. Structure and Entry: Enveloped viruses fuse with host cells, releasing their genetic material
    3. Gene Expression: Viral DNA is uncoated in the nucleus, triggering mRNA production
    4. DNA Replication: Replication via rolling circle mechanism yields genomic DNA
    5. Assembly and Release: Nucleocapsids assemble in the nucleus, acquiring an envelope during budding through the nuclear membrane
    6. Distinctive Assembly: Herpesviruses acquire their envelope during nuclear membrane budding
  • Pathophysiology of Herpesviruses

    1. Neurovirulence: invades the nervous system
    2. Latency: establishes latent infection in nerve ganglia
    3. Reactivation: induced by various stimuli, leads to recurrence
    4. Differential reactivation: HSV-1 oral; HSV-2 genital
    5. Impact of immunity: crucial defense; spreads in immunocompromised
    6. Global transmission: humans only; close contact spread
    7. Transmission: via mucosal surfaces or skin cracks
    8. Inactivation: easily inactivated; rare aerosol spread
  • Virulence of Herpesviruses

    1. HSV Cell Cycle
    2. Initial steps of HSV primary infection
  • Associated Diseases

    • Herpes Simplex virus 1 - Oral herpes
    • Herpes Simplex virus 2 - Genital herpes
    • Varicella Zoster Virus - Chickenpox & Shingles
    • Epstein-Barr Virus - Mononucleosis
    • Cytomegalovirus - Pneumonia, retinitis, & hepatitis
  • Oral herpes is caused by Herpes Simplex Virus 1
  • Genital herpes is caused by Herpes Simplex Virus 2
  • Chickenpox & Shingles are caused by Varicella-Zoster Virus
  • Mononucleosis is caused by Epstein-Barr Virus
  • Chicken pox symptoms

    • Blisters
  • Vaccines

    • Chicken pox: Varivax (live attenuated)
    • Shingles: Zostavax
  • Mononucleosis virus: Epstein-Barr Virus
  • Mononucleosis virus genus

    Lymphocryptovirus
  • Mononucleosis virus infects

    Epithelial cells of the skin and mucous membranes
  • Mononucleosis virus causes

    Acute infectious mononucleosis
  • Mononucleosis virus associated with
    • Burkitt lymphoma
    • Hodgkin and non-Hodgkin lymphomas
    • Nasopharyngeal carcinoma
    • Gastric Carcinoma
    • Other lymphoproliferative disorders (in immunodeficient individuals)
  • Pneumonia, retinitis, and hepatitis virus: Cytomegalovirus (DS-DNA, enveloped)
  • Cytomegalovirus is the most common cause of congenital infection

    Which can lead to severe abnormalities
  • Cytomegalovirus may be symptomatic if
    • Newborn: congenital CMV
    • Infants: infected through breast milk
    • Immunocompromised individuals: undergone transplant (organ, bone marrow, or stem cell), or have HIV
  • Hepadnaviridae

    A family of viruses that infect the liver