Section 21.4 Emerging Infectious Diseases Slide 1 of 15 Objectives Define the term emerging disease. Identify five reasons why diseases emerge. Section

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Section 21.4 Emerging Infectious Diseases

Objectives

Define the term emerging disease.

Identify five reasons why diseases emerge.


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Health Stats The map shows how dengue fever, a viral disease carried by mosquitoes, has spread since 1960.

Should the United States be concerned about dengue fever? Explain.

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• An epidemic (ep uh DEM ik) is an unusually high occurrence of a disease in a certain place during a certain time period.

What Is an Emerging Disease?

• When an epidemic affects many areas of the world, it is sometimes called a pandemic.

• An emerging disease is an infectious disease that has become increasingly common in humans within the last 20 years or threatens to become more common in the near future.

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Click above to go online.

For: Updates on modern epidemics

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• Diseases can emerge when humans come into contact with infected animals; pathogens become resistant to existing drugs; or people lack appropriate immunizations.

Why Do Diseases Emerge?

• The increased frequency of international travel and a global food supply can enable emerging diseases to spread very quickly.

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• Some diseases that are common in animals can spread to humans.

Contact With Infected Animals

• There have been recent cases in Asia in which people have become sick after being exposed to infected birds.

• Scientists fear that another deadly flu epidemic could result if the virus takes on a form that can spread easily between people.

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• Some diseases are caused by pathogens that can mutate, or change, over time.

Drug Resistance

• Sometimes these mutations result in a strain, or type, of pathogen that no longer responds to medicine.

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• Diseases that were common many years ago can pose a threat again if people don’t get the proper immunizations.

Lack of Immunization

• The polio virus remains a threat in several Asian and African countries because many people in those countries have not received the vaccine.

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• Globalization refers to the fact that people around the world are no longer geographically isolated from each other.

International Travel

• Not only can people travel much more easily, but so can any pathogens that live in their bodies.

• World travelers could spread the pathogen around the world in a short amount of time.

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• Food also travels around the world.

Global Food Supply

• If a pathogen is present in a food product, it can spread quickly.

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Vocabulary

epidemic An unusually high occurrence of a disease in a certain place during a certain time period.

emerging disease An infectious disease that has become more common within the last 20 years or threatens to become more common in the near future.

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QuickTake Quiz

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For: Chapter 21 self test

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End of Section 21.4

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Section 21.4 Emerging Infectious Diseases Slide 1 of 15 Objectives Define the term emerging disease. Identify five reasons why diseases emerge. Section