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Exam 1 Review - Global Infectious Disease, Viruses, Bacteria, Cells, DNA, RNA, Genome, Parasites, Mosquito-Borne Diseases, Prions

Exam 1 Review: Comprehensive Study Guide

Examination Logistics

  • Date: Tomorrow, Monday 9/29.

  • Materials: Bring a pen.

  • Instructions: Remember to put your name and your TF's name on every page.

  • Preparation: Check out the practice exam.

Lecture 1: Global Infectious Disease

  • Definition: Human diseases caused by pathogens that spread across the globe.

  • Classes of Infectious Agents and Examples:

    • Malaria: Caused by a parasite, transmitted via mosquito.

    • Tuberculosis (TB): Caused by a bacterium, treatable by antibiotics, but significantly, bacteria can adapt and evade treatments, leading to resistance.

    • Smallpox: Caused by a virus, had a large impact throughout history.

    • vCJD ("mad cow disease"): Caused by a prion, transmitted via BSE-infected beef.

  • Exacerbating Factors: Global infectious diseases are often exacerbated by poverty.

    • Examples: The surge of diseases after the collapse of the USSR and persistent malaria epidemics in Africa.

  • Eradication Strategies: We can eradicate global diseases via global vaccination campaigns.

    • Examples: Smallpox (successfully eradicated) and Measles (achieved significant reduction, though not complete eradication globally).

Lectures 2 & 3: Viruses

  • Historical Discovery: Ivanovsky showed that a non-bacterial agent caused disease in Tobacco plants, demonstrating the existence of something smaller than bacteria. The Chamberland filter (established in 1884) filtered out all known bacteria, implying the pathogenic agent was smaller.

  • Viral Morphology (Structure): Viruses are composed of:

    • Nucleic Acid (either DNA or RNA).

    • Protein.

    • Lipids (sometimes, forming an envelope).

  • Viral Classification (Baltimore Classification): Viruses are classified based on their genetic material and replication strategy. There are 7 main groups:

    • Group 1: dsDNA (e.g., Smallpox).

    • Group 2: +ssDNA (e.g., Parvovirus).

    • Group 3: dsRNA (e.g., Rotaviruses).

    • Group 4: +ssRNA (e.g., Coronaviruses).

    • Group 5: -ssRNA (e.g., Measles).

    • Group 6: +ssRNA-RT (Retroviruses, e.g., HIV).

    • Group 7: dsDNA-RT (e.g., Hepatitis B).

  • Viral Replication Process (Example: Influenza Virus in an Epithelial Cell):

    • Viruses exhibit cell-type specificity and differing replication mechanisms, with varying lethality.

    • 1. Attachment: The influenza virus becomes attached to a target epithelial cell via specific receptors.

    • 2. Penetration: The cell engulfs the virus through endocytosis.

    • 3. Uncoating: Viral contents (nucleic acid and associated proteins) are released into the host cell cytoplasm.

    • 4. Biosynthesis: Viral RNA enters the nucleus, where it is replicated by the viral RNA polymerase, and viral proteins are synthesized.

    • 5. Assembly: New viral particles are assembled from newly synthesized viral components.

    • 6. Release: New viral particles are made and released into the extracellular fluid. Notably, the host cell, in this case, is often not immediately killed but continues to produce new virus particles.

  • Influenza Virus Evolution (Genetic Variation):

    • Antigenic Drift: Characterized by the accumulation of small mutations within the viral genome. This leads to minor antigenic changes with the potential for recurrent epidemics.

    • Antigenic Shift: Involves genetic reassortment, often when two different influenza viruses (e.g., avian and human strains) infect the same host cell, leading to exchanges of genetic material. This results in major antigenic changes with the potential for pandemics (e.g., a