Chapter Outlines

Chapter 6      Mechanisms of Viral Entry and Spread of Infection in the Body

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6.1 Preferred Routes of Entry
  • Viruses gain entry into the host and then target specific cell types.
    • Respiratory tract
    • Gastrointestinal tract
    • Genital tract
    • Conjunctiva (eyes)
    • Crossing the placenta-may cause teratogenic effects
Viruses and Congenital Infections
  • See Table 6-1
Viral Infections that Enter Through the Respiratory Tract
  • See Table 6-2 and Table 6-3
Viruses that Enter by the Gastrointestinal Tract
  • See Table 6-4
Oral-fecal Transmission
Viruses that cause STDs
  • See Table 6-5
Other (Rare) Routes of Entry
  • Skin
  • Transplants
  • Blood transfusions
  • Iatrogenic
Viruses that Enter Through the Skin
  • See Table 6-6
Viral Infections of the Eyes
Viral Infections and Transplants/Screening the Blood Supply
  • See Table 6-7 and Table 6-8
Iatrogenic Induction
  • Infections generated by a physician.
    • e.g surgical procedures using contaminated equipment/tools.
    • CJD and vCJD (prions diseases, Chapter 19)
6.2 Mechanisms of Viral Spread of Pathogenesis
  • Replication and infections within the host
  • Localized infections
  • Primary viremia
  • Systemic infections-lymph vessels
Target Organs
  • Skin (e.g. Papillomaviruses)
  • Lungs (respiratory tract viruses e.g. Influenza, SARS-CoV)
  • Liver (hepatitis viruses)
  • Brain (neurotropic viruses e.g varicella zoster)
Skin Rashes
  • See Table 6-11
CNS: Crossing the Blood-Brain Barrier
  • Blood-brain barrier is semi-permeable
Neural Entry
  • Structure of neurons
6.3 Patterns of Diseases
  • Acute, nonpersistent infections
  • Acute infections followed by a persistent infection
  • Chronic infections-latency
  • Slow infections (e.g TSEs, chapter 19)
Latent Infections
  • See Table 6-12
6.4 Virus Exit: Shedding
  • How do viruses get from one host to another?
  • Viruses usually shed through routes of entry
    • Mucus
    • Saliva
    • Semen
    • Feces
    • Skin abrasions
    • Breast milk
    • Cervical secretions
    • Urine
    • Viremia-blood
  • What about viruses that infect the brain?
  • Most brain viruses affect other target organs and are perpetuated and shed that way.
  • Environmental survival of viruses
    • Nonenveloped vs. enveloped viruses
    • Human viruses in water
    • Intestinal viruses

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