1. 2.2 Viruses, Viroids, Prions

2. Some viruses contain DNA, while others contain RNA

3. Spread of Viruses Regional outbreak – Epidemic
Global outbreak - Pandemic

4. Role of Viruses Some cause diseases with relatively mild symptoms
Chicken pox, common cold
Some are much more deadly
AIDS, Hanta, rabies, Ebola
Some increase risk of cancer (e.g. HPV  cervical cancer)
Important historically for the control of populations

6. Infection
Most viruses can only infect one type of host cell, or a few closely related hosts
Viruses that affect bacteria are called phages (bacteriophages)
The capsid of phages don’t enter the host cell, while the capsids of animal viruses do enter the cell

8. Vaccinations
Parts of a virus or a weakened form of a virus is injected into an individual
Response of the body creates immunity against the virus
Obstacles to vaccination
Structure of virus
Rapid changes and mutations in virus
Too many strains

9. A quick note on childhood vaccines
There is zero supporting evidence that childhood vaccines lead to autism or any other disorders
Not getting vaccinated reduces herd immunity

10. Gene Therapy
Because viruses infect host cells so effectively, scientists can use them to deliver drugs or a desired section of DNA
Chemotherapy
Correcting a genetic disorder
Genetic engineering

11. Viroids and Prions Viroids – small, infectious pieces of RNA
Plant pathogens
Prions – infectious proteins
E.g. mad cow disease
Both are very poorly understood