3 Viral Pathogenicity

🦠 Viral Pathogenesis | How Viruses Cause Disease Welcome to this Medical Virology lecture on Viral Pathogenesis, where we explore how viruses enter the human body, interact with host cells, spread through the body, evade immune defenses, and ultimately cause disease. This lecture connects the cellular effects of viral infection with the mechanisms occurring in the infected patient, providing a clear overview of the major steps involved in viral disease development. 📚 Topics Covered: 🔹 Introduction to Viral Pathogenesis 🔹 Viral pathogenesis at the cellular and patient levels 🧬 Effects of Viral Infection on Host Cells 🔹 Cell death and inhibition of cellular macromolecule synthesis 🔹 Formation of multinucleated giant cells (MGCs) 🔹 Malignant transformation by oncogenic viruses 🔹 Silent and latent infection 🩺 Stages of Viral Infection 🔹 Incubation period 🔹 Prodromal period 🔹 Specific-illness / clinical period 🔹 Recovery period 🦠 Stepwise Viral Pathogenesis 🔹 Transmission and portal of entry 🔹 Viral replication and cellular damage 🔹 Spread between host cells and organs 🔹 Role of the immune response 🔹 Viral persistence 🔄 Routes of Viral Transmission 🔹 Horizontal transmission 🔹 Respiratory aerosols, saliva, blood and semen 🔹 Fecal–oral transmission 🔹 Vertical transmission from mother to offspring 🔹 Transplacental transmission 🔹 Transmission during delivery and breastfeeding 🔹 Animal-to-human transmission 🔹 Reservoir hosts and insect vectors 🚪 Major Portals of Entry 🔹 Respiratory tract 🔹 Gastrointestinal tract 🔹 Skin 🔹 Genital tract 🔹 Blood 🔹 Transplacental route 🌐 Localization and Spread of Viral Infection 🔹 Localized viral infections 🔹 Systemic viral infections 🔹 Poliovirus as an example of systemic viral spread 🛡️ Viral Immunopathogenesis & Immune Evasion 🔹 Role of cytotoxic T cells and antibodies 🔹 Immune-mediated tissue damage 🔹 Antibody-complex deposition 🔹 Viral interference with cytokines and immune mediators 🔹 Reduction of MHC Class I expression 🔹 Antigenic variation 🔹 Inhibition of complement activation ♻️ Persistent Viral Infections 🔹 Mechanisms of viral persistence 🔹 Integration into host DNA 🔹 Immune tolerance 🔹 Cell-to-cell spread 🔹 Immunosuppression 🔹 Rapid antigenic variation 🔹 Chronic carrier infection 🔹 Latent infection 🔹 Slow virus infection 🎯 By the end of this lecture, students should be able to: • Explain the major mechanisms by which viruses cause cellular injury. • Describe the stages of viral infection in an infected patient. • Identify the major routes of viral transmission and portals of entry. • Differentiate localized from systemic viral infections. • Explain the role of host immunity in viral pathogenesis. • Describe major mechanisms used by viruses to evade host immune defenses. • Explain how viruses establish persistent infections. • Differentiate chronic carrier, latent and slow viral infections. 🎓 Recommended for: Clinical Laboratory Sciences (CLS) Students • Medical Laboratory Science Students • Medical Students • Microbiology & Virology Students • Pharmacy Students • Nursing Students • Health Sciences Students 📌 Subject: Medical Virology / Medical Microbiology 🦠 Topic: Viral Pathogenesis