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Understanding Epidemiology
Infectious Agents and Preventative
Measures
What is an Infectious Disease?

“Any disease caused by invasion by a
pathogen which subsequently grows and
multiples in the body.”

Pathogen = any disease-causing agent.
Categories of Infectious Agents
• Metazoa
• Protozoa
• Fungi
• Bacteria
• Viruses
• Ricketssia
• Prions
Disease Transmission

Two types of transmission:
1) Direct
o
o
Transmission mechanism in which the infectious
agent is transferred directly into the body.
Examples: Touching, kissing, or biting.
2) Indirect
o
o
Transmission mechanism in which the infectious
agent is transferred to the person by a vector or
fomite.
Examples: Airborne, vector-borne, or vehicleborne.
Disease Transmission (Direct)

Types of Direct Transmission:
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Person-to-Person
Animal-to-Person
Mother-to-Unborn Child
Droplet
Direct Exposure
Disease Transmission (Indirect)

Types of Indirect Transmission:
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Vector-borne
Fomite
Vehicle-borne
Airborne
Natural Barriers to Infection
Skin
 Reflexes

◦ Coughing and Sneezing
Tears
 Acidic pH in the stomach
 Mucous membranes

Host Response

What is host response?
◦ Reaction of a living system to some material.

Why is this relevant to epidemiology?
◦ Leads to clues about the disease.
◦ Leads to effective interventions to help
prevent and stop spread of disease.
Where Germs are Found
Germs live all around us at home, school,
and work.
 Common places to find germs include:
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Soil
Air
Water
Food
Animals
People
High-touch surfaces, like doorknobs and
telephones
Effective Preventative Measures

Requires looking at your habits, lifestyles,
and surroundings.
◦ Practice good personal hygiene.
◦ Treat all bodily fluids as potentially infectious.
◦ Use protective barriers when exposed to
infectious agents.
◦ Maintain a clean home and work
environment.
◦ Store and cook foods at the proper
temperature.
Effective Preventative Measures

80% of all infectious diseases are
transmitted by touch.

Frequent and proper hand washing is key
to preventing the spread of infection.
Proper Hand Hygiene
Proper Hand Hygiene

Wash your hands
after:
◦ Using the restroom.
◦ Changing a diaper.
◦ Coughing, sneezing, or
blowing your nose.
◦ Handling a pet.
◦ Preparing or handling
uncooked foods.

Wash your hands
before and after:
◦ Cleaning cuts or
abrasions.
◦ Changing bandages.
◦ Changing soiled linens.
Proper Hand Hygiene

Step 1: Use large amounts of warm,
running water and liquid soap to lather
hands and wrists.
◦ Scrubs all surfaces of hands and fingers for 1520 seconds.
◦ Bar soap can harbor germs that cause
infection, so it is important to use liquid soap
when possible.
Proper Hand Hygiene

Step 2: Rinse hands well with clean,
running water.
◦ Important to rinse with your hands pointed
down to prevent the rinse water from
running up your arms.

Step 3: Dry with a disposable paper
towel.
Proper Hand Hygiene

Step 4: Shut off faucet using the paper
towel as a barrier between your clean
hands and the faucet handle.

Step 5: Use a skin moisturizing cream
regularly to prevent cracks in the skin,
which can serve as entry points for germs
to cause infection.
Proper Hand Hygiene

When soap is not available, use an
alcohol-based gel (at least 60% alcohol) to
sanitize hands.

Do not use an alcohol rub when hands
are visibly soiled.
Resources

“Where are Germs Found?” Lysol. http://lysol.org/home-and-family/helpprotect-your-family/where-are-germs-found/.

“Break the Cycle of Infection – Tips That Will Keep You Healthy.”
http://aids.about.com/od/expertadvice/a/infection.htm.