1. Chapter 19-3: Diseases Caused by Bacteria and Viruses
Bacteria and viruses are everywhere in nature, but only a few cause disease.
Disease-causing agents are called pathogens.

2. Bacterial Disease in Humans
Many bacteria live on and within our bodies.
Growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities and producing disease.

3. How do bacteria cause disease?
They damage the cells and tissues of the infected organism directly by breaking down the cells for food.
Or they release toxins (poisons) that travel throughout the body interfering with the normal activity of the host.

4. Preventing Bacterial Disease
Many bacterial diseases can be prevented by vaccines (a preparation of weakened or killed pathogens).
When injected into the body, a vaccine may prompt the body’s immunity to the disease.

5. Treating Bacterial Disease
If infection occurs, drugs can be used to destroy bacteria.
These drugs include antibiotics, which are compounds that block the growth and reproduction of bacteria.
A reason for increased human life expectancy is an increased understanding of how to prevent and cure bacterial infections.

6. Viral Disease in Humans
Viruses produce disease by disrupting the body's normal equilibrium.
How do viruses cause disease?
Lytic: viruses can attack and destroy certain cells in the body, causing symptoms of the disease.
Lysogenic: other viruses cause infected cells to change patterns of growth and development.

7. Viral Disease Prevention/Treatment
Vaccines are the best protection against viral diseases, but only work if used before an infection begins.
Viral diseases cannot be treated with antibiotics.
Symptoms may be treated with over-the-counter medicines.

8. Bacterial Diseases
Viral Diseases
Lyme disease
Tetanus
Tuberculosis
Bacterial meningitis
Strep throat
Common cold
Influenza
AIDS
Chicken pox
Hepatitis B
West Nile

9. 40-1: Infectious Disease
Disease: any change, other than an injury, that disrupts the normal function of the body
Can be inherited, caused by materials in the environment, or produced by pathogens (disease causing agents).
Can be inherited, caused by materials in the environment (ex: cigarette smoke), or produced by pathogens (bacteria, viruses, fungi).
First observed by French chemist Louis Pasteur and German bacteriologist Robert Koch

10. The Germ Theory of Disease
Idea that infectious diseases are caused by microorganisms, or germs
Observed by French chemist Louis Pasteur and German bacteriologist Robert Koch

11. Koch’s Postulates
Series of guidelines used to identify the microorganism that causes a specific disease
These rules are important because identifying pathogens that cause disease is the first step toward prevention or cures.

12. The Postulates (or rules)
The pathogen should always be found in a sick organism, not a healthy one.
It must be isolated and grown in the lab.
When injected in a new host, it should cause the same original disease.
The injected pathogen should be isolated from the new host and identical to the original pathogen.
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13. Agents of Disease
For many pathogens, the human body provides just the right conditions for growth.
Agent
Example
Viruses
Common cold, flu, warts
Bacteria
Botulism, Anthrax
Protists
Malaria, African Sleeping Sickness
Worms
Schistosoma
Fungi
Athletes foot, ringworm
Suitable temperature, watery environment full of nutrients

14. Worms: Schistosoma Protists: Trypanosoma Fungi: athlete's foot
Fungal spores
Fungi: athlete's foot

15. How Diseases Are Spread
Coughing, sneezing, or physical contact
Contaminated food or water
Vectors: infected animals that carry pathogens from person to person
Malaria, lyme disease, west nile virus, rabies

16. Fighting Infectious Diseases
Antibiotics: compound that blocks the growth and reproduction of bacteria (no effect on viruses)
Over-the-Counter Drugs: treat only the symptoms, but do not actually treat the cause of the infection