Chapter Outlines
Chapter 1 Introduction to Viruses
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1.1 Viral Impact on the Environment, Research and Disease
- Viruses have an impact on all forms of life.
- There are beneficial roles of viruses in life
Viruses and Aquatic Ecosystems
- Bacteriophages are abundant in fresh and saltwater
- Bacteriophages free up organic matter so that new life can be generated.
Lytic Bacteriophages and Nutrient Cycling
Hershey-Chase Blender Experiment
- Provided evidence that DNA was the hereditary material
Bacteriophage Therapy
- Bacteriophages can be used to treat infections
Gene therapy
- Uses viruses to deliver genes in order to treat genetic diseases
Vaccine Development
- People have been attempting to prevent infectious diseases for centuries
- Edward Jenner is credited with the first scientific attempt at intententional inoculation
Viruses and Cancer
- Cervical cancer (papillomaviruses)
- Liver cancer (hepatitis B and C viruses)
1.2 Early Virus Studies
Characteristics of Viruses
- Viruses are small (nm in size)
- Can pass through filters that trap most known bacteria.
- Completely dependent upon host cell
- Contains one species of nucleic acid
Viral genome consists of DNA or RNA
- Viruses possess receptor-binding protein
- Genome may be infectious
- Retroviruses insert genome into cellular chromosome
Visualizing Viruses: Electron Microscopy
- Electron microscopes are powerful tools for:
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- studying how viruses are assembled
- studying the structure of fragile viruses
- the rapid detection and diagnosis of viral infections
Theories of Viral Origin
- Influenza viruses fall from outerspace?
- Regressive theory
- Cellular origin theory
- Coevolution theory
1.3 Viruses in History: Great Epidemics
- Influenza
- Poliomyelitis
- Acquired Immunodeficiency Syndrome (AIDS)
1.4 Recent Viral Outbreaks
- Foot and Mouth Disease, 2001, 2007 United Kingdom
- Hantavirus: Four Corners Disease, 1993
- West Nile Virus (WNV), New York City, 1999
- Norovirus outbreaks
Where did WNV come from?
- Infected birds migrate?
- Infected birds displaced during storms?
- Legal and illegal importation of sick birds
- Birds are vagrants on ships or other transportation
- WNV can infect many species (Table 1.1)
1.5 Smallpox: Ancient Agent of Bioterrorism
- Biological weapons have been used for centuries
- Disease-causing viruses can be used to kill large populations of plants, animals and humans
- New vaccines, antivirals and diagnostic tests needed to prevent the threat of bioterrorism
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