SCI W2

Discussion 2 - Concepts of Infectious Disease

Topic/Instructions

Read Chapter 2 first. Then come to this discussion.

I have set the discussion up around the general topic of Concepts of infectious disease. Since the chapter in the textbook is so full of important concepts, it would be difficult to narrow it down to a single topic for discussion. So I have posted this introduction and 5 separate subtopics.

Each student should choose one of these subtopics for your major post. 

Take an active role in presenting this topic to the other students. 

Explain the concept in your own words, or develop it further using a relevant example. You should then read the comments of other students in the other subtopics, and respond to at least one in every subtopic that has a primary comment in it. That allows you to develop one subtopic in an active sense, but learn about the others by being drawn into them through other people's posts. 

You should write well thought out primary comments on at least one of the points below (150-200 words). Then, you should make well thought-out comments to your classmates' comments, at least one in every subtopic that is being developed. 

Subtopic 1: Factors that affect the spread of epidemics - Part 1

Question: Explain the following statement:

Epidemiology is the Study of the relationship between an infectious agent and its host population

A balanced host/parasite relationship must exist: 

The virus can deplete host, but if virus completely eliminates the host, it will become extinct.

Subtopic 2: Factors that affect the spread of epidemics - Part 2

Question: Explain how the interaction between these factors are relevant to the transmission of AIDS. For example, which of these factors are most critical to the transmission of HIV. Which aren't. 

1. Total number of hosts

2. Host’s birth rate

3. Rate at which new susceptible hosts migrate into population

4. Number of susceptible uninfected hosts

5. Rate at which disease can be transmitted from infected to uninfected hosts

6. Death rate of infected hosts

7. The number of infected hosts who survive and become immune or resistant to further infection

Subtopic 3: Acute versus Chronic Infections

Question: Compare the definitions of Acute Infections and Chronic Infections below. Based on what you know about HIV/AIDS at this point, which description most closely matches AIDS? Explain your answer, using evidence from the book to support your position. 

What is an acute infection?


1. Produces symptoms and makes a person infectious soon after infection.

2. The infected person may:                                                                                                                                                                                          transmit the disease

die from the infection

recover and develop immunity

3. the acute microorganism

STRIKES QUICKLY

infects entire group (small group)

dies out

What is a chronic infection?


Person may never show symptoms

Person continues to carry infectious agent at a low level

Does NOT mount an effective immune response

Subtopic 4: Controlling infectious disease

Question: Explain what herd immunity is and how it works. Use an example from either the book or the internet to explain your position. 

Herd immunity = when all, or nearly all susceptibles are immunized, no new infection can occur. Agent can be eradicated from the population.

Subtopic 5: Modern concepts of Infectious Disease and Koch's Postulates

From the Oxford Dictionary:

Definition: postulate

verb |ˈpäsCHəˌlāt| [ with obj. ]

1 suggest or assume the existence, fact, or truth of (something) as a basis for reasoning, discussion, or belief: his theory postulated a rotatory movement for hurricanes | [ with clause ] : he postulated that the environmentalists might have a case.

a thing suggested or assumed as true as the basis for reasoning, discussion, or belief: perhaps the postulate of Babylonian influence on Greek astronomy is incorrect.

 Robert Koch was a physician/scientist in the 1800s who studied the transmission of infectious disease. He proposed 4 postulates, also known as Koch's Postulates (p. 12-13) help control the spread of infectious disease.  He proposed that a microorganism can be considered to be a disease if it fulfills certain criteria or conditions. These are listed on p. 12 in the textbook. The book also goes on to describe how these postulates helped to prevent the spread of the plague pandemic in the late 1800s. 

Question: Using what you learned from the movie "And the Band Played On", described the ways that Koch's postulates helped scientists to identify what was going on with this new acquired immune deficiency syndrome (AIDS), and to help it from exploding completely out of control.

Module 2 Reflection

In each module, we'll have a final discussion to "reflect" on what we learned this week. Here you can post commentary on something that we discussed, how a concept would apply to a particular situation, etc. For Week 2, why don't you each just tell me a new insight that you learned about infectious disease. You can make multiple posts if you'd like, or pose questions for additional discussions. be creative. Everyone should make at least one meaningful comment, and that should be at least 100 words.