Download 35.3 Fighting Infectious Disease

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35.3 Fighting Infectious Disease
Lesson Objectives
Distinguish between active immunity and passive immunity.
Describe how public health measures and medications fight disease.
Describe why patterns of infectious disease have changed.
Lesson Summary
Acquired Immunity You can acquire immunity without having a disease.
▶ Vaccination is the injection of a weakened or mild form of a pathogen to cause immunity.
▶ Active immunity results from vaccines or natural exposure to an antigen.
▶ Passive immunity forms when antibodies are introduced into the body. It lasts only until
the immune system destroys the foreign antibodies.
Public Health and Medications In 2005, less than 5 percent of human deaths were
caused by infectious diseases. This statistic is the result of two major factors.
▶ The field of public health provides services that help monitor food and water supplies and
promote vaccinations and healthy behavior.
▶ The development and use of many new medications, particularly antibiotics and antiviral
drugs, has saved many lives by helping to cure infectious diseases.
New and Re-Emerging Diseases Since 1980, many new diseases have appeared and
several diseases once thought to have been eradicated have recurred. There are two main
reasons for these changes.
▶ Interactions with exotic animals have increased.
▶ The misuse of medications has caused diseases that were once under control, such as
tuberculosis and malaria, to evolve resistance to many antibiotics.
Acquired Immunity
1. What was the origin of the term vaccination? Explain why this name was given.
The term comes from the Latin word vacca that means “cow.” The name was given to
honor the work of English physician Edward Jenner who used fluid from cowpox sores
to produce immunity to smallpox in humans.
2. How does a vaccine work?
A vaccine stimulates the body to make memory B cells and memory T cells for a
specific antigen to strengthen and quicken the body’s response to repeated infections.
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3. What type of immunity do vaccinations produce?
active immunity
4. What type of immunity does a mother pass on to her infant while breastfeeding?
passive immunity
5. Why is passive immunity only temporary?
The body’s immune system destroys the antibodies because it sees them as foreign.
6. Complete the Venn diagram comparing the two types of immunity and writing the
correct word or words on the lines provided.
Active Immunity
Long-term ability
of immune system
to respnd to
antigens
Passive Immunity
Short-term
Can result
from natural or
deliberate
.
ability to fight off
infections due
to introduced
antibodies
exposure.
.
Public Health and Medications
For Questions 7–11, complete each statement by writing the correct word or words.
7. Promoting childhood vaccinations and providing clean drinking water are two
public health activities that have greatly reduced the spread of many infectious
diseases.
8. Compounds that kill bacteria without harming the host cells are called
9. The first antibiotic to be discovered was
10.
Antiviral
penicillin
antibiotics
.
.
drugs inhibit the ability of viruses to invade cells or multiply within cells.
11. How did Alexander Fleming discover the first antibiotic?
Fleming saw that the growth of bacteria was inhibited by a mold called Penicillium
notatum. He isolated a compound made by the mold and determined that it killed
the bacteria.
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New and Re-Emerging Diseases
For Questions 12–16, write the letter of the correct answer on the line at the left.
C
12. Which of the following is NOT considered to be a major cause of new or
re-emerging diseases?
A. misuse of medications
B. merging of human and animal habitats
C. vaccination
D. trade in exotic animals
C
13. Which is an example of an infectious disease that was eliminated by public health
measures?
A. avian influenza
B. hantavirus
C. smallpox
D. West Nile virus
A
14. How are monkeypox and SARS thought to have started in humans?
A. by animal trade for pets and food
B. antibiotic resistance
C. the clearing of new areas of land in the tropics
D. by the merging of human and animal habitats
B
15. Malaria and tuberculosis are two examples of diseases that have
A. been totally eliminated from the human population.
B. evolved resistance to many antibiotics.
C. increased because of a lack of understanding of how vaccines work.
D. recently been discovered in the United States.
D
16. Failing to follow vaccination recommendations are thought to be responsible for
the comeback of
A. Ebola.
B. influenza.
C. Lyme disease.
D. measles.
17. After being vaccinated, many children are treated for fever. This is not considered a
danger or problem. Why might this happen?
SAMPLE ANSWER:
Vaccines are often weakened forms of an antigen. The body reacts to
it by attacking it. Vaccination depends on the body recognizing, attacking, and
remembering the antigen. Fever is one of the first immune responses. So, a fever
after vaccination is evidence that the body is reacting strongly to the antigen.
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35.4 Immune System Disorders
Lesson Objectives
Explain what happens when the immune system overreacts to harmless pathogens.
Describe how HIV is transmitted and how it affects the immune system.
Lesson Summary
When the Immune System “Misfires” Sometimes, the immune system overreacts to
otherwise harmless antigens. Three types of disorders are caused in this way.
▶ The most common immune-system disorders are allergies, which occur when antigens
enter the body and bind to mast cells. The mast cells release histamines, which increase
the flow of blood and fluids to the area. This causes allergy symptoms.
▶ Allergic reactions in the respiratory system can cause asthma, a dangerous chronic disease
in which the air passages narrow and breathing becomes difficult.
▶ When the immune system makes a mistake and attacks the body’s own cells, an
autoimmune disease results. Autoimmune diseases include Type I diabetes, rheumatoid
arthritis, and lupus.
HIV and AIDS In the 1970s, clusters of cases of opportunistic diseases—diseases that attack
people with weakened immune systems—led to the discovery of a new disease called acquired
immunodeficiency syndrome (AIDS).
▶ Research revealed that AIDS is an infectious disease caused by human immunodeficiency
virus (HIV). HIV attaches to receptors on helper T cells. Once inside the cells, HIV copies
itself and the new viruses infect more helper T cells.
▶ HIV infection gradually leads to the death of more and more T cells. When a person’s T
cell count drops to about one-sixth the normal level, the person has AIDS.
▶ HIV can only be transmitted through contact with infected blood, semen, vaginal
secretions, or breast milk.
When the Immune System “Misfires”
For Questions 1–5, complete each statement by writing the correct word or words.
1. An overreaction of the immune system to antigens of pollen and other harmless
allergy
substances is called a(n)
.
2. Sneezing, a runny nose, and watery eyes are symptoms of the inflammatory response
in the respiratory system.
3. Drugs called antihistamines counteract the effects of
mast cells.
histamines
produced by
4. A dangerous condition that affects the respiratory system and can be caused by allergies is
asthma
called
.
5. Examples of environmental triggers for allergic reactions include tobacco smoke,
pollution, molds, and pet dander.
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6. What is an autoimmune disease?
It is a disease in which the body’s immune system fails to recognize “self” and attacks
cells and compounds in the body as if they were pathogens.
7. Describe the advantage and disadvantage of treating an autoimmune illness such as lupus.
Treatment of lupus with an immunosuppressant medication can help alleviate symptoms,
because it suppresses the immune response. However, because the medications suppress
the body’s normal immune response, they make the body more vulnerable to infections.
8. Complete the table about autoimmune diseases.
Autoimmune Diseases
Autoimmune Disease
Organ or Tissue That Is Attacked
Type I diabetes
Insulin-producing cells of the pancreas
Rheumatoid arthritis
Connective tissues around the joints
Lupus
Organs and tissues throughout the body
HIV and AIDS
9. What does AIDS stand for?
It stands for “acquired immunodeficiency syndrome.”
10. What is the term that describes diseases that attack people with a weakened immune
system?
opportunistic diseases
11. List four body fluids that can transmit AIDS.
A.
blood
B.
semen
C. vaginal secretions
D.
breast milk
12. What behaviors prevent people from being infected with HIV?
Abstinence from sexual activity and abstinence from intravenous drug use prevent
infection by HIV.
13. Why is curing HIV infection so challenging? Explain your answer.
HIV can be treated, making it possible to survive with the infection for many years.
However, a vaccine that can prevent HIV infection has not been developed yet because
HIV mutates and evolves so rapidly.
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14. Complete the flowchart that summarizes the HIV infection process.
Contact with infected semen, vaginal secretions, or blood.
HIV attaches to host cell membranes with specific surface molecules.
Viral coat fuses with cell membrane; viral RNA enters the cell.
Reverse transcriptase uses viral RNA to make viral DNA.
Viral DNA enters nucleus, attaches to host DNA, and makes viral RNA.
Viral mRNA directs the host cell to assemble viral proteins.
New viruses bud off of host cell membrane and infect more cells.
15. What is the key difference between an immunodeficiency disease and an autoimmune
disease? Provide an example of both types of disease in your response.
SAMPLE ANSWER:
In an immunodeficiency disease, such as AIDS, the immune system itself
is damaged or destroyed. While, in autoimmune disease, such as type 1 diabetes, it’s
the immune system that damages or destroys organs or tissues.
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Chapter Vocabulary Review
Use the diagram to answer Questions 1–3.
1. The structure labeled A in the diagram
represents a(n) antibody .
2. The structure labeled B in the diagram
antigen
represents a(n)
.
B.
3. On the lines below, describe the interaction
that occurs between antibodies and antigens.
A.
Antibodies recognize and bind to antigens
tolabel foreign or infected cells for destruction.
For Questions 4–7, match the definition with the correct term.
Term
Definition
C
4. Animal that carries a pathogen from person to person
A. asthma
D
5. A disease that is transmitted from animals to humans
B. vaccination
A
6. Chronic respiratory disease in which the air passages become
narrower than normal
C. vector
B
7. Injection of a weakened or mild form of a pathogen to
produce immunity
D. zoonosis
For Questions 8–10, write the letter of the correct answer on the line at the left.
A
8. Chemicals that block the replication of viruses in the body are called
A. interferons.
C. allergies.
B. histamines.
D. antigens.
B
9. Which chemicals are produced during the inflammatory response?
A. interferons
C. allergies
B. histamines
D. antigens
D
10. An elevated body temperature that helps stop the growth of pathogens is a(n)
A. vector.
C. allergy.
B. zoonosis.
D. fever.
For Questions 11–13, complete each statement by writing the correct word or words.
11. A change to the physiology that disrupts normal body functions and is caused by a
microorganism is called a(n)
infectious
disease
.
12. The part of the immune response that depends on the action of macrophages and several
types of T cells is called cell-mediated immunity.
13. The part of the immune response that depends on the action of B cells and antibodies
circulating in the blood and lymph is called
humoral
immunity.
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In the Chapter Mystery, you learned about a
group of people in one part of Connecticut
who came down with Lyme disease. Lyme
disease is spread by certain kinds of ticks.
But many infectious diseases are spread
directly from person to person.
THE SEARCH
FOR A CAUSE
Learning
Infectious Diseases in History
Smallpox is a deadly, highly-contagious disease that was once common throughout Europe,
Asia, and North Africa. The war against smallpox began in the late 1700s when the British
physician Edward Jenner developed a smallpox vaccine. In the 1900s, there was a worldwide
effort to administer the vaccine on a global scale. By 1980, the disease had been effectively
eradicated. One of the last serious smallpox outbreaks occurred in Eastern Europe in 1972.
The following article describes what happened during one of the last battles against this
devastatingly contagious disease.
SMALLPOX’S LAST STAND
Every year, millions of people travel to
the city of Mecca in Saudi Arabia. In 1972,
on his way back from the Middle East, one
man traveled through an area known to
have smallpox. He returned to his village in
Kosovo, Yugoslavia with the smallpox virus.
Oddly enough, the pilgrim only became
slightly sick. But he indirectly passed the
virus along to a man named Ljatif Muzza,
who lived in a neighboring town. When
Muzza became sick, he went to the local
hospital, where they could not diagnose
what was wrong with him. (No one
recognized smallpox because there had
been no outbreaks for many years.) The
local hospital sent him to a larger facility,
which then sent him to the main hospital
in the capital city, Belgrade. Muzza died
shortly thereafter. But in his journey from
hospital to hospital, he had infected 38
other people with smallpox, eight of whom
would die as well.
At this time, Yugoslavia was ruled by a
Communist dictator named Josip Broz, who
called himself “Tito.” He used his dictatorial
powers to take drastic measures to stop
the smallpox outbreak. He declared martial
law and the province in which Muzza had
lived was blocked off; no one was allowed
in or out. People who had been infected
were quarantined in special hospitals.
Anyone who had come into contact with
infected individuals—10,000 people in
all—were given smallpox vaccinations and
quarantined in hotels, under army guard.
Around the country, public events were
banned and barbed wire and barricades
were used to stop people from traveling—
and from spreading the disease. The
outbreak died out after a few weeks, and
only 35 people died.
Continued on next page ▶
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Science and Health Literacy
1. How was smallpox eradicated from the global population?
The development of a smallpox vaccine and the worldwide effort to administer the
vaccine effectively eradicated the disease on a global scale.
2. Why did it take so long for doctors to recognize Muzza’s disease as smallpox?
The doctors were not familiar with smallpox; there had been no outbreaks in many
years.
3. What information in the article indicates that smallpox is spread directly from person to
person?
The fact that so many people whom Muzza came in contact with got sick, indicates
that smallpox is spread from person to person.
4. What drastic measures were taken to control the outbreak?
Sick people were quarantined; those who came in contact with them were vaccinated
and also quarantined; travel was restricted.
5. In the United States, children are no longer given the smallpox vaccine. Why do you think
this is the case?
SAMPLE ANSWER:
Smallpox is spread from person to person. Because the disease has been
eradicated, there is little chance that the disease can spread from person to person.
Controlling an Epidemic
The skills used in this activity include information and media literacy, communication
skills, creativity and intellectual curiosity, and social responsibility.
Epidemic diseases are on people’s minds much more today than they were in 1972.
Smallpox has been eliminated, but others, such as avian flu and SARS, are possible threats.
Your state government most likely has plans in place to deal with possible epidemics or
pandemics. If you live in a large city, municipal officials may have been planning as well.
Interview the appropriate officials to find out what plans and procedures are in place to
protect the public in the event of an epidemic. Then use the information to write a magazine
article describing your government’s plans.
Students’ articles should provide detailed descriptions of plans in place and should
contain quotes from state and/or local officials.
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