Immunity –Disease – any change that disrupts body’s internal regulation (homeostasis) –Pathogen – anything that causes disease  Ex. Virus, bacteria, fungi, protists

How do scientists determine cause of disease? Koch’s Postulates: Koch’s Postulates: 1.Pathogen must be found in all individuals with disease 2. Isolate pathogen from diseased individuals & grow in pure culture without any other organisms

Koch’s Postulates: 3.Test pathogen grown in culture on new host. New host must get disease. 4. Isolate pathogen from new host & compare to original pathogen

Exceptions to Koch's Postulates Some bacteria will not grow in artificial cultures Some bacteria will not grow in artificial cultures – Ex. Syphilis Viruses need host cell to replicate. So, culture must contain living tissue. Viruses need host cell to replicate. So, culture must contain living tissue.

Where do pathogens hide? There must be a continual source or reservoir of disease organisms. There must be a continual source or reservoir of disease organisms.

1. Human Body – major reservoir for human disease causing pathogens  Healthy Carriers – people who do not have symptoms of illness & pass on disease unknowingly Where do pathogens hide?

 People in the incubation period of disease. –1 st stage of disease, symptom- free, pathogens are multiplying in body –Ex. Cold, flu Where do pathogens hide?

2. Animals – vectors for influenza, rabies, Lyme 3. Non-living Reservoirs – soil & water Ex. Botulism, tetanus, anthrax, intestinal diseases Where do pathogens hide?

How are pathogens transmitted? 1. Direct contact – STD’s, cold, flu 2. Indirect contact - By an object like money, cell phones, door knobs  Prevented by washing hands frequently

How are pathogens transmitted? 3. Airborne – inhaled via microscopic droplets in air exhaled from infected organism 4.By animal bite – mosquitoes, ticks, bats

What causes disease symptoms? Viruses – take over host cell and kill cell Viruses – take over host cell and kill cell Bacteria / Fungi – produce toxin (poison) Bacteria / Fungi – produce toxin (poison) –Toxins move through blood & cause damage by killing cells, stopping protein function, producing fever/spasms

Who looks for patterns of disease? CDC – Center for Disease Control CDC – Center for Disease Control –Monitor disease outbreaks across the country

 Endemic disease – constantly present in population Ex. Cold  Epidemic – many people in one area are sick with same disease at the same time Ex. Flu  Pandemic – worldwide epidemic

How are diseases treated? Antibiotics – kill or stop bacterial diseases Antibiotics – kill or stop bacterial diseases Antivirals – stop viral diseases, specifically HIV, herpes, hepatitis and some strains of influenza Antivirals – stop viral diseases, specifically HIV, herpes, hepatitis and some strains of influenza Immune System – built in defense system against all foreign pathogens Immune System – built in defense system against all foreign pathogens