Spread of Infectious Diseases

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What is an outbreak?• According to the CDC, an “outbreak” is

the occurrence of more cases of disease than normally expected within a specific place or group of people over a given period of time.

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WHAT IS AN EPIDEMIC?

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What is an epidemic? • An epidemic is when an unusually large

number of people in a community get a disease at the same time. Examples of epidemic diseases include typhus, influenza, the Black Death, malaria, and smallpox.

• a prefix occurring in loanwords from Greek, where it meant “upon,” “on,” “over,” “near,” “at,” “before,” “after”

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What causes an epidemic? • Infected food and water • Increased virulence of the disease -

Sometimes the pathogen (germ) that causes a disease may change and become more virulent. This means that it can more easily infect people and make them sick.

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What causes an epidemic? • Introduction of a new disease• Lower resistance to a disease • Natural disasters and wars

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HOW ARE DISEASES SPREAD?

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How does a disease spread? • Insects - Insects can carry diseases and

transmit them from person to person. Examples of insect-borne diseases include the bubonic plague and malaria.

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How does a disease spread? • Airborne transmission - Infection can

also travel through the air, usually when a person coughs or sneezes. Examples of airborne diseases include influenza, measles, and tuberculosis.

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How does a disease spread? • Food and water - Some diseases can

be spread through infected food or water. Examples include cholera, dysentery, and typhoid fever.

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How do they end? • Fewer hosts – • Over time, the disease finds less and

less hosts it can easily attack. Eventually the epidemic slows down and comes to an end.

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How do they end?

• Seasonal – The flu, for example, is spread more easily during the winter and tends to die out come spring time.

• Fewer carriers – • An example of this is malaria that is

transmitted by mosquitoes. Mosquitoes become inactive during the cold weather or winter.

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WHAT IS A PANDEMIC?

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What is a pandemic? • A pandemic is an epidemic that has

spread across a large region, typically across multiple continents or worldwide.

• Prefix “pan” means “ALL”

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Six Stages of a Pandemic • The World Health Organization (WHO)

describes six stages of a pandemic virus:• 1. The virus is found in animals, but not in

humans.• 2. The virus has been found in humans.• 3. There are small clusters of the disease

found, but it is not spreading rapidly.

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Six Stages of a Pandemic • 4. The virus is being passed from

human-to-human and there are community outbreaks of the disease.

• 5. The virus has spread to at least two countries. A full-fledged pandemic is imminent.

• 6. The disease is now classified as a full-fledged pandemic.

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WHAT IS AN EXAMPLE OF A PANDEMIC?

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Curbing the Spread of Disease• Quarantine

– Identifying the contaminated people & separating them

– Are rarely used today– Drawbacks

• identifying all the sick people• not all sick people show symptoms• Doesn’t block all ways of spreading germs

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Curbing the Spread of Disease• Your Immune System

• Controlling Vectors– Ex. Spraying mosquitos to control Malaria

• Sanitation– Keeping food, water & environment clean

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Curbing the Spread of Disease• Antiseptics

– chemicals that kill germs– Used to sterilize medical tools

• Washing Hands

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CDC and WHOCDC - The Centers for Disease Control and Prevention (CDC) is a federal agency that conducts and supports health promotion, prevention and preparedness activities in the United States, with the goal of improving overall public health.

WHO - The World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health. It was established on 22 July 1946 headquartered in Geneva, Switzerland.

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Herd ImmunityWhen a critical portion of a community is immunized against a

contagious disease, most members of the community are protected

against that disease because there is little opportunity for an

outbreak. Even those who are not eligible for certain

vaccines—such as infants, pregnant women, or

immunocompromised individuals—get some protection because

the spread of contagious disease is contained. This is known as

"community immunity."

The principle of community immunity applies to control of a variety

of contagious diseases, including influenza, measles, mumps,

rotavirus, and pneumococcal disease.

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IDENTIFY WAYS TO CURB THE SPREAD OF DISEASE?

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Bubonic Plague

https://www.youtube.com/watch?v=rZy6XilXDZQ

The Black Death Song

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WHY IS THIS IMPORTANT TO ME?

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What if it Happened?• What if?• https://www.youtube.com/watch?v=baOl

T-1yY4A• While viewing the video, write 5

ideas/facts/thoughts

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