online homework 20 infection and disease

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Infectious Diseases: Unit 1

Why should we care about infectious diseases.

The goal of this unit is to improve students’ understanding on the impact that infectious diseases had and still have on societies, and to introduce the factors responsible for infectious diseases. The unit begins by engaging the students by presenting the impact of infectious diseases from historical and current perspective. It continues with introduction to microbes as the infectious agents and focus on their structure and functions, especially in relation to microbes’ infectivity and pathogenicity. The unit is completed by introducing the roles of different protective barriers that the human body has to fight off invaders.

The flu, do we overreact?

This lesson is intended as an ‘engage’ as well as to address the larger question: Why should we care about infectious disease? You will capture student interest by stimulating a discussion focused on what makes a disease infectious. The flu is then used to illustrate the potential impact infectious diseases can have. Students are asked to question the importance of flu shots. The students revisit this question again after watching a video about the Spanish flu pandemic of 1918.

How infectious disease has molded history—including ours

This lesson is intended to emphasize that infectious diseases shape history and our day-to-day lives. You will guide the students using the Poodwaddle Clock to assess current rates of infection and mortality caused by select globally significant diseases. Then, you will explore how infectious diseases have impacted history.

As a homework review before the jigsaw in Lesson 1.3 students may need to be reminded of the general structure of a bacterial cell. I thought this might be a good website reminder. It will help with the fluidity of the lesson. —Teacher who piloted this lesson at Boston Latin School

What is an infectious agent? (1) What bacteria need to make us sick

This lesson has two purposes. First, it is intended to demonstrate how infectious disease influences our day-to-day habits as we try minimize our exposure to pathogens. Second, the students will be introduced to bacterial structures and their functions in disease.

What is an infectious agent? (2) What viruses do to make us sick

This lesson has two purposes: First, it introduces viruses by exploring relative sizes of bacteria and viruses and how this contributes to their modes of action. The lesson then extends the previous focus on bacterial structures by showing how viral structures also play important roles in infectivity and disease.

So why aren’t we always sick? Our body’s defenses

We are covered in bacteria and exposed to viruses all the time, but we rarely get sick. Why? Students will develop their understanding of sterility and the notion that the interior of the body is sterile while the exterior is non-sterile. This will involve a new concept: the outside of the body includes all areas that contact the environment, including the intestinal lumen. Based on these ideas, students will then identify host barriers designed to protect against infection.

Teacher Prep: Unit 1 Lesson Overview Videos

In the YouTube embed below, click the order listing in the upper right to toggle the display for the full playlist.

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1: Introduction to Infectious Diseases

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Examples of reading assignment :

Introduction to infectious diseases vocabulary

any abnormal bodily condition that impairs functioning and can usually be recognized by signs (what can be seen/felt e.g., redness, swelling) and symptoms (what patients “feels” e.g. nausea, malaise, pain).

Figure 1.1 : Child infected with smallpox/variola virus. (Public Domain;  CDC/James Hicks )

Infectious disease

disease caused by colonization of host organism by pathogenic microbes

• -pathos =suffering genic =to make
• -pathogenic microbes e.g. prions, viruses, bacteria, protozoa

EID=Emerging Infectious Diseases:

\described as infectious diseases appearing /”emerging” within the last 20-30 years. e.g. zoonotic avian influenza, Ebola

Figure 1.2: Influenza virus model http://www.cdc.gov/flu/images.htm

• Included as EID’s are “ re-emerging infectious diseases ”, diseases which had decreased in prevalence at one time in history and now are once more spreading through human populations.
• The Institute of Medicine (IOM) also includes the recently evolved antibiotic-resistant pathogens as causes of EID’s. -e.g. MRSA/ Methicillin Resistant Staphylococcus aureus , MDR-TB/Multi-Drug Resistant Tuberculosis.

An organism/agent (e.g. virus, bacterium, helminth) which lives at the expense of another (the host). The terms parasite and pathogen are sometimes used interchangeably.

from Greek patho =suffering, An agent/organism which causes disease/harm to another organism (the host). pathogenic : capable of causing disease e.g. pathogenic microbe compared to non-pathogenic microbe

Greek oikos =house - logy = study of : the study of interactions between organisms and their environment

Infectious Disease Medical ecology

the study of the interactions between h ost, pathogens and environment leading to infectious disease .

The living together of two (or more) dissimilar organisms. 3 types of symbiotic relationships:

• mutualism : both symbiotic partners benefit (e.g. non-pathogenic E. coli living in your intestinal tract)
• commensalism : one partner benefits, the other neither benefits nor is harmed, e.g. Staphylococcus aureus living harmlessly in your nose)
• parasitism : one partner (the parasite/pathogen) benefits at the cost of th other partner (the host is harmed). e.g. Staphylococcus aureus causing an infection of a cut on your hand; E. coli causing a bladder infection

-Note: as indicated with Staphylococcus aureus and E.coli , symbiotic relationships can change !

Opportunistic pathogen

A microbe which normally does not cause disease but given special circumstances, may cause disease. e.g. E.coli causing bladder infection / cystitis or Pneumocystis jirovecii causing pneumonia in someone with HIV/AIDS

Microbial pathogens

Pathogens/parasites too small to be seen with the “naked eye” / not using magnifying instrument, e.g. prions , viruses, bacteria, protozoa.

Macroscopic parasites

parasites which can be seen with the “naked eye”/without magnification. The general categories:

• ectoparasites : parasites which live/feed on the outside (“ecto-“) of the body. Many are blood-feeders , e.g. insects including fleas, mosquitoes, lice; arachnids including ticks.
• endoparasites : parasites which live within (“endo-“) the host.e.g. “worms” or helminths such as Ascaris lumbricoides

Arthropod vectors

Many of the blood-feeding ectoparasites act as arthropod vectors, organisms which transfer microbial pathogens between hosts.

• -eg. Mosquitoes are vectors of West Nile virus and Plasmodium/ malaria.
• * arthropod = “jointed foot”; invertebrates (lack backbones) with segmented bodies and jointed limbs; have “exoskeletons:” -e.g. insects, arachnids

Figure 1.3: A mosquito as a vector. http://www.cdc.gov/features/stopmosq...toes_456px.jpg

Agents of infectious diseases

Acellular agents Cellular organisms

Determinants of Infectious Disease

To cause an infectious disease, a pathogen must be able to:

• Initially be transported to host: food, water, sex, arthropod vectors, aerosols, animal bites, blood, congenital
• Adhere to, colonize or invade the host
• Multiply (grow) or complete its life cycle on or in the host
• Initially evade host defense mechanisms
• Possess the mechanical, chemical or molecular ability to damage the host.
• Leave host, invade new host

Discussion questions and study guide questions for quizzes and exams.

Prepare for lecture 2, TURN-IN your answers at the start of lecture 2, make sure your name is on your homework sheet. + 5 points

People will be asked to answer these questions during our class discussion in lecture 2.

• What are “infectious diseases”? Provide 1 example
• What are EID’s, Emerging Infectious Diseases? Provide 2 examples
• 3. Medical ecology explores how interactions between pathogens, hosts and the environment lead to infectious diseases. Draw and label a medical ecology Venn Diagram indicating pathogen, host, environment and infectious disease.
• 4. Describe pathogen, host and environment factors which could influence prevalence of infectious diseases by filling in the table below:

5. Define/describe the following terms and provide a specific example of each.

6. Do an online computer search for “the political ecology of infectious disease ”.

What is your definition of the political ecology of infectious diseases ? Provide a specific example.

Contributors

Karen Carberry-Goh, D.V.M., Ph.D. ( Sacramento City College )

• AQA Trilogy

Infection and response

Part of Combined Science

Communicable diseases - AQA

Pathogens are disease-causing viruses, bacteria, fungi or protists, which can infect animals and plants. Humans have an immune system, which can defend them from pathogens.

Treating, curing and preventing disease - AQA

Some diseases can be treated with antibiotics. Vaccinations allow protection against specific diseases, but the level of protection depends on the amount of people vaccinated.

Sample exam questions - infection and response - AQA

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.

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