Infectious Disease

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What is Disease?

• Disease– Any change in the body, other than injury, that

disrupts the normal functions of the body– Disease has many causes

• Bacteria• Viruses• Environmental Factors (cigarette smoke, pollution)• Genetics

Koch’s Postulate

• Koch said:– Disease is caused by

microorganisms and NOT by curses, evil spirits or night vapors

– Yes, for thousands of years, people believed that diseases were caused by those things.

Infectious Disease

• Infectious = can be passed from person to person

• Pathogens – Cause disease– EX:

• Bacteria• Viruses• Protists• Worms

Bacteria

• Single Celled living organisms– Asexual reproduction– Multiply by themselves

• Can easily be seen with a microscope!!

• Live & breed in warm, moist environments

• Prokaryotes: no nucleus

Bacteria and Humans

• Most bacteria = harmless

• Good for humans!– many places on our bodies – Intestines…digestion

Bacteria as Pathogens

• Bacteria as Pathogens– Break down tissues– Release toxins– EX:

• Streptococcus (Strep Throat)• Diptheria• Botulism• Anthrax• E. coli (found in food)

Bacteria

Treatments for Bacterial Infection

• Antibiotics– Kill bacteria, but not body

cells– Interfere with the cellular

processes of the bacteria– One antibiotic will kill

many different kinds of bacteria

– Examples: Penicillin, Amoxicillin

Virus• 1000 times smaller than

bacteria!!– Cannot be seen with a

microscope

• Cannot live or reproduce on their own– Must invade a host cell– Contain RNA or DNA but

none of the equipment to reproduce

Virus• Pathogenic

• Mutate often

• Examples:– Common cold– Influenza– Smallpox– Warts– HIV

Virus

Treatments for Viral Infection

• Best treatment:– Rest– Water– No help from Doc!

• Antibiotics are NOT effective against viruses because the virus live within your own body’s cells.

Why you feel sick when you have an infection

• Symptoms caused by your body’s response to the infection– Fever

• kill the pathogen

– Vomiting, Runny nose, coughing • physically remove the pathogen

– You feel tired because your body is working overtime fighting the infection

In Review• An Infectious Disease is

– Disease that can be passed from person to person

• A Pathogen is– A disease causing agent

• Bacteria– Single-celled living organisms– Killed by Antibiotics

• Virus– Tiny particles, need host cell in order to

replicate– Antibiotics are INEFFECTIVE