1.05 - Introduction to viruses Dr Lauren McNeill
Page 1: Introduction
Dr. Lauren McNeill is a Lecturer in Biosciences and Deputy Director of Admissions at Lancaster University.
Overview of the lecture on viruses.
Page 2: Aims of the Lecture
Review important infectious pathogens and sources of infections.
Define and understand viruses as unique microorganisms.
Discuss classification methods for viruses.
Explore the diseases caused by viruses.
Discuss treatment options for viral infections.
Consider future implications of viral diseases.
Page 3: Quick Recap
Summary of points covered regarding viruses.
Page 4: Sources of Infection
Endogenous Sources: Infections from the host's normal flora.
Exogenous Sources: Infections transmitted from an external source.
Page 5: Important Infectious Pathogens
Categories of infectious pathogens include:
Bacteria
Viruses
Fungi
Parasites
Page 6: Focus on Viruses
Specific focus on viruses within the medical curriculum at Lancaster University Medical School.
Page 7: Commonality of Individuals
Notable historical figures: Mary Berry, Franklin D. Roosevelt, Jack Nicklaus, and others.
Page 8: Polio Overview
Polio was eliminated in most countries since effective vaccines were developed in the 1950s.
Page 9: Details on Polio
Polio is caused by the Picornaviridae RNA virus:
Transmitted via faecal-oral route.
Primarily affects children under 5 years.
1 in 200 infections can lead to irreversible paralysis.
WHO aims for polio eradication by 2026.
Page 10: Historical Figures
Commonality of notable figures: Elizabeth I, Abraham Lincoln, Joseph Stalin, etc.
Page 11: Smallpox Eradication
Smallpox was eradicated, with the last wild case in 1977; remaining strains kept in labs.
Page 12: Links Between Figures
Questioning what links the discussed individuals.
Page 13: Rabies Overview
Classical rabies virus, carried by warm-blooded animals, results in fatal encephalomyelitis once symptoms appear.
Rhabdovirus infection via infected animal bites.
Page 14: Pandemic Impact
Inquiry into death tolls surpassing those of World War I.
Page 15: Spanish Flu Pandemic
Spanish Flu (1918-1919) infected approximately 1/3 of the global population, causing more deaths than WW1.
Page 16: Child Mortality Statistics
Investigation on what caused more child deaths than road accidents in 2019.
Page 17: Measles Outbreak in Samoa
2019 outbreak: 6000 cases and 83 deaths due to declined MMR vaccine uptake.
Vaccination programme reinstated, bringing the outbreak under control.
Page 18: Measles Overview
Measles caused by Morbillivirus:
Transmitted via the airborne route.
Highest mortality among children under 2 years.
Natural infection leads to lifelong immunity.
Page 19: Annual Case Statistics
Influenza has around 1 billion cases annually.
Page 20: Seasonal Influenza Statistics
3-5 million cases of severe illness; 290,000 to 650,000 respiratory deaths annually.
Disproportionate death rates in young children in developing countries.
Page 21: Importance of Viruses
Viruses play a significant role in global health issues.
Page 22: Structure of Viruses
Introduction to basic virus structure and components.
Page 23: Basics of Virus Structure
A virus particle, or virion, usually has a viral genome in a protein capsid.
Viral genomics are crucial for infection and classification processes.
Page 24: Virus Structure Details
Viruses are metabolically inert and lack cellular structures.
Differentiation between enveloped and non-enveloped viruses.
Page 25: Important Notes on Viruses
Key points:
Viral genomes only function post-infection.
Viruses exploit the host's protein synthesis pathways.
Page 26: Virus Classification
Viruses classified by several factors:
Type of nucleic acid in the genome.
Size, structure, symmetry of the virion.
Replication methods and nucleic acid strands.
Page 27: Classification Specifics
Key elements for viral classification:
Type of nucleic acid (DNA or RNA).
Virion size/structure and replication mode.
Page 28: Viral Genomes Types
DNA Viruses: Typically double-stranded (except Parvovirus).
RNA Viruses: Generally single-stranded, with exceptions (e.g., Reovirus).
Page 29: Baltimore Classification of Viruses
Seven groups based on nucleic acid types and other characteristics.
Page 30: Examples of Viral Genomes
Comparative classification of various viral families and their characteristics.
Page 31: Hierarchical Virus Classification Example
Order: Herpesvirale | Family: Herpesviridae | Subfamily: Alphaherpes virus | Genus: Simplex virus | Species: Herpes Simplex virus (HSV).
Page 32: DNA Viruses Overview
Focus on DNA viruses causing human diseases and relevant examples.
Page 33: Specific DNA Viruses
Notable human pathogens in the DNA virus category:
Poxviridae: Cowpox
Herpesviridae: Herpes simplex, Varicella zoster (chickenpox)
Adenoviridae, Papovaviridae, Hepadnaviridae, Parvoviridae.
Page 34: RNA Viruses Overview
Insight on RNA viruses that affect humans.
Page 35: Specific RNA Viruses
Notable RNA viruses causing human diseases and related examples:
Orthomyxoviridae: Influenza A/B/C
Paramyxoviridae: Mumps, Measles
Rhabdoviridae: Rabies, etc.
Page 36: Additional RNA Viruses
More RNA viruses relevant to human health, emphasizing those included in vaccination programs.
Page 37: Routes of Virus Transmission
Types of viral transmission pathways:
Respiratory route – airborne (flu, Covid).
Direct contact (Herpes simplex virus, chickenpox).
Insect bites (arboviruses).
Sexual/injection (blood-borne viruses).
Faecal/oral route (enteric viruses).
Page 38: Nature of Virus Testing
Testing for viral infections is complex; conventional methods such as agar plates are ineffective.
Modern testing focuses on detecting viral DNA or proteins.
Page 39: Viral Infections Mechanism
Example of common cold caused by rhinovirus:
High virus concentration is dispersed through nasal secretions.
Importance of hand hygiene in transmission prevention.
Page 40: Immune Response to Infection
Overview of immune response upon virus infection, particularly with rhinovirus:
Initial innate immune response actions.
Page 41: Subsequent Immune Response
Discussion of adaptive immune response producing antibodies against reinfection.
Page 42: Herpes Simplex Virus
Causes cold sores; characteristics of transmission and latent infection.
Page 43: Varicella-Zoster Virus
Focus on chickenpox and shingles:
Dormancy and potential for future reactivation in individuals.
Page 44: Subclinical Infections
Clarification on human viruses:
Some cause subclinical or asymptomatic infections rather than overt disease.
Page 45: Lifecycle of Viruses
Overview of the lifecycle stages of a virus:
Attachment, penetration, replication, assembly, release.
Page 46: Replication of DNA Viruses
Description of DNA virus replication processes related to the Baltimore classification.
Page 47: Replication of RNA Viruses
Explanation of RNA virus replication processes aligned with the Baltimore classification.
Page 48: Importance of Virus Lifecycle Understanding
Key factors for viruses:
Ability to enter target cells.
Capacity for efficient replication.
Ability to exit host cells.
Page 49: Antiviral Treatments
Challenges in developing antiviral treatments.
Increasing number of antiviral agents, particularly for specific viral groups.
Page 50: Mechanisms of Antiviral Action
Various mechanisms by which antiviral agents operate:
Inhibition of DNA synthesis with examples like acyclovir.
Page 51: Preparing for Future Pandemics
Emphasis on global surveillance and technological readiness for rapid vaccine development.
Page 52: Summary of Learnings
Key takeaways regarding viral structure and treatment, including genome types and antiviral therapy goals.
Page 53: Suggested Further Reading
References for deeper understanding:
Mims' Medical Microbiology and Immunology
Clinical and Diagnostic Virology guide.