Science & Technology in Action

1st Edition

The Fight Against Infectious Diseases

Health Service Executive

This lesson defines the meaning of a pathogen and examines the nature of viruses. It describes the reproductive process of viruses and the function of vaccination in protecting against them.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

What is an infectious disease?
In this lesson we will look at the causes and treatment of infectious diseases as a result of viruses. Disease is an unhealthy condition of the body due to disruption of its normal functioning. Diseases may be genetic or acquired through accidents at birth, through malnutrition or injury. At the present time we still don’t know the cause of many diseases. About one third of all deaths each year are due to pathogenic diseases.

What is a pathogen?
A pathogen is an infectious disease-causing organism. Pathogens can be viruses, bacteria or fungi. All viruses are pathogenic as they are obligate intracellular parasites. A parasiteis an organism that lives with, and gains nourishment from, another organism causing it harm. Intracellular means that it lives within thecell. Obligate means that the virus must be with its host to gain nourishment and to reproduce. Although many human diseases are caused by viruses most viruses are harmless to us.

Is a virus a living organism?
An organism is a living structure composed of one or more cells - based on this definition a virus is not a living organism. Viruses are non-cellular and the typical virus structure is a surrounding wall of protein protecting the genetic material that can be DNA or RNA.

Quiz questions

  1. A pathogen is a disease-causing organism. true
  2. All diseases are caused by pathogens. false
  3. Viruses are extracellular parasites. false
  4. Viruses are unicellular organisms. false
  5. The genetic material of viruses may be DNA or RNA. true
  6. Excretion is not a characteristic of viruses. true
  7. A virus can 'attack' any live cell. false
  8. Some bacteria are now resistant to particular antibiotics. true
  9. All cancers result from genetic mutation. false
  10. Viruses can cause genetic mutation in their host cell. true
  11. Activated T cells produce and secrete antibodies. false
  12. After infection all the activated B cells are destroyed. false
  13. Vaccines produce memory B cells without causing the disease. true