1. 19-3 Diseases Caused By Bacteria and Viruses
Photo Credit: ©National Institute for Biological Standards and Control, England/Photo Researchers, Inc.

2. Diseases Caused by Bacteria and Viruses
Bacteria and viruses are everywhere in nature, but only a few cause disease.
Disease-causing agents are called

3. Bacterial Disease in Humans
Louis Pastuer was the first to show that bacteria cause disease.
Growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities and producing disease.
But HOW do bacteria cause disease?

4. Bacterial Disease in Humans
Bacteria produce disease in one of two general ways.

5. Bacterial Disease in Humans
Bacteria cause disease in the body. Some of the diseases caused by pathogenic bacteria are listed in the table.

6. Bacterial Disease in Humans
Many bacterial diseases can be prevented by vaccines.
A vaccine is
When injected into the body, a virus may prompt the body’s immunity to the disease.
Immunity is the body's ability to destroy new pathogens.
Normal immunizations include:

7. Bacterial Disease in Humans
If infection occurs, drugs can be used to destroy bacteria.
These drugs include antibiotics, which are
A reason for increased human life expectancy is an increased understanding of how to prevent and cure bacterial infections.

8. Controlling Bacteria
The easiest way to combat bacterial pathogens is preventative care accomplished by controlling the growth
3 methods used to control bacterial growth, include:

9. Sterilization Sterilization:
Most bacteria are killed by prolonged high temperatures.

10. Disinfectants Disinfectants :
They are used to clean rooms where bacteria may flourish.

11. Food Storage and Processing
Bacteria can cause food to spoil.
Refrigerated food:
Boiling, frying, or steaming can:
Canned foods is VERY good at staying sterile because it is often heated and then sealed.

12. Viral Disease in Humans
Like bacteria, viruses produce disease by disrupting the body's normal equilibrium.
Viruses can attack and destroy certain cells in the body, causing symptoms of the disease.
Other viruses cause infected cells to change patterns of growth and development.

13. Viral Disease in Humans
Viral diseases CANNOT
Vaccines are often the best protection against most diseases.
Most vaccines work only if used before an infection begins.
Symptoms may be treated with over-the-counter medicines.
Smallpox is :
Other examples include:

14. Viral Disease in Humans
Viruses cause disease in the body. Some of the diseases caused by viruses are listed in the table.

15. Viral Disease in Plants and Animals
Viruses produce serious animal diseases including foot-and-mouth disease.
Many viruses infect plants but have a harder time doing so. Why?
These viruses pose a serious threat to many crops.

16. Viroids and Prions
Other virus-like particles that can cause disease are viroids and prions.
Viroids:
Prions:

17. Viroids
Viroids:
Viroids enter an infected cell and synthesize new viroids.
They then disrupt the cell’s metabolism and stunt the growth of the entire plant.

18. Prions Prions: Prions cause disease by:
Eventually, there are so many prions in the nerve tissue that cells become damaged.
Example: