Pathogens and Disease Overview

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Questions and Answers

What is the primary difference in how active and passive immunity are acquired?

Active immunity is when the body produces its own antibodies, while passive immunity is when antibodies are transferred from another source.

Provide an example of natural passive immunity and how it occurs?

Maternal antibodies transferred from mother to child through breast milk are an example of natural passive immunity.

What are monoclonal antibodies and what is their primary mechanism of action?

Monoclonal antibodies are lab-engineered antibodies that bind to very specific targets, for example, on cancer cells or pathogens.

What is the primary cause of transplant rejection?

<p>Transplant rejection occurs because the immune system recognizes the transplanted organ as 'non-self' and attacks it.</p> Signup and view all the answers

What can occur if a person receives an incompatible blood transfusion?

<p>An incompatible blood transfusion can lead to hemolysis, which is the destruction of red blood cells and can cause severe reactions.</p> Signup and view all the answers

Explain why antibiotics are not effective against viral infections.

<p>Antibiotics work by targeting structures and processes unique to bacteria, they do not work on viruses.</p> Signup and view all the answers

What is the general term for a microorganism that can cause disease?

<p>pathogen</p> Signup and view all the answers

How does penicillin inhibit bacterial growth?

<p>Penicillin inhibits bacterial growth by blocking the synthesis of bacterial cell walls.</p> Signup and view all the answers

Give an example of a disease caused by a protozoan.

<p>Malaria</p> Signup and view all the answers

Who discovered the first antibiotic and what was it?

<p>Alexander Fleming discovered the first antibiotic, penicillin, in 1928.</p> Signup and view all the answers

What bodily fluid is NOT a mode of transmission for HIV?

<p>saliva</p> Signup and view all the answers

What is the name of the oily secretion on the skin that inhibits microbial growth?

<p>sebum</p> Signup and view all the answers

What condition results in a person's blood not clotting properly?

<p>Hemophilia</p> Signup and view all the answers

Name one physical barrier that prevents pathogens from entering the human body.

<p>skin or mucus or cilia</p> Signup and view all the answers

What is the process by which white blood cells engulf and destroy pathogens?

<p>phagocytosis</p> Signup and view all the answers

What is the general term for the type of medication (e.g., chloroquine) that treats Malaria?

<p>antimalarial drugs</p> Signup and view all the answers

Describe one mechanism by which bacteria become resistant to antibiotics.

<p>Bacteria can produce enzymes that deactivate antibiotics, modify target sites to prevent antibiotic binding, or increase efflux pumps to remove antibiotics.</p> Signup and view all the answers

What is the role of high contact rates in the spread of a disease?

<p>High contact rates facilitate the rapid spread of a disease.</p> Signup and view all the answers

What is the focus of study in epidemiology?

<p>Epidemiology focuses on the distribution of diseases and the factors that influence outbreaks.</p> Signup and view all the answers

What key action did John Snow take to address the Broad Street cholera outbreak?

<p>John Snow removed the handle of the Broad Street water pump.</p> Signup and view all the answers

In the SIR model, what does 'I' represent?

<p>In the SIR model, 'I' represents the infected individuals who are actively spreading the disease.</p> Signup and view all the answers

What does an Râ‚€ value less than 1 indicate about disease spread?

<p>An Râ‚€ value less than 1 indicates that the disease is likely to die out.</p> Signup and view all the answers

Name two public health measures that were used during the COVID-19 pandemic to control the spread of the virus.

<p>Lockdowns, social distancing, mask-wearing, hand hygiene, and vaccination programs.</p> Signup and view all the answers

Why was it important to 'flatten the curve' during the COVID-19 pandemic?

<p>Flattening the curve slowed infection rates to prevent healthcare systems from being overwhelmed.</p> Signup and view all the answers

Besides reduced transmission, what were two negative impacts of lockdowns and social distancing?

<p>Economic and mental health impacts.</p> Signup and view all the answers

Which measure was more effective at reducing infections: hand hygiene or mask-wearing?

<p>Mask-wearing.</p> Signup and view all the answers

What was the primary goal of 'flattening the curve' during a disease outbreak?

<p>To prevent overwhelming the healthcare system.</p> Signup and view all the answers

Name two key strategies, mentioned in the text, used to achieve the goal of flattening the curve.

<p>Social distancing and mask mandates.</p> Signup and view all the answers

What triggers the shift of the 'S' group to the 'I' group in the SIR model?

<p>Contact rates with an infected person.</p> Signup and view all the answers

What is one important limitation of the basic SIR model?

<p>It assumes all individuals are equally likely to be infected.</p> Signup and view all the answers

Why is the SEIR model useful for modeling diseases like COVID-19?

<p>The SEIR model includes an 'Exposed' category, which accounts for the incubation period of the disease. This is important because COVID-19 has a significant incubation period, where individuals are infected but not yet infectious.</p> Signup and view all the answers

What distinguishes the SIRS model from the SIR model?

<p>The SIRS model allows recovered individuals to become susceptible again, unlike the standard SIR model where recovered individuals are permanently immune. This is useful for diseases where immunity wanes, such as the flu.</p> Signup and view all the answers

How can spatial models help in tracking global pandemics?

<p>Spatial models incorporate geographic movement, which allows for tracking how a disease spreads across regions and countries. This is particularly useful in predicting the spread of global pandemics.</p> Signup and view all the answers

What are the various ways zoonotic diseases spread from animals to humans?

<p>Zoonotic diseases can spread through direct contact with infected animals, consuming contaminated animal products, or via vectors like mosquitoes and ticks that transmit pathogens from animals to humans.</p> Signup and view all the answers

Why is post-exposure prophylaxis (PEP) for rabies most effective before symptoms appear?

<p>PEP for rabies, which includes a vaccine, must be administered before the onset of symptoms because once rabies symptoms appear, the disease is typically fatal. PEP helps the body develop immunity before the virus reaches the brain.</p> Signup and view all the answers

What is the function of lysosomes within phagocytes in the context of fighting pathogens?

<p>Lysosomes contain enzymes that break down pathogens that have been engulfed by phagocytes.</p> Signup and view all the answers

How does histamine contribute to the swelling seen in an infected area?

<p>Histamine increases the permeability of blood vessels, causing fluid to leak and accumulate in the tissues.</p> Signup and view all the answers

What principle did Edward Jenner demonstrate with his smallpox vaccine?

<p>He demonstrated that exposure to a milder, related virus (cowpox) can provide immunity against a similar, but more dangerous virus (smallpox).</p> Signup and view all the answers

What is the key difference in the targets of the humoral and cell-mediated responses in the adaptive immune system?

<p>The humoral response targets extracellular pathogens while the cellular response targets infected or abnormal cells.</p> Signup and view all the answers

How do phagocytes differentiate between 'self' and 'non-self' cells?

<p>Phagocytes recognize 'self' cells by detecting MHC markers; 'non-self' cells lack these markers and are recognized by foreign antigens, triggering phagocytosis.</p> Signup and view all the answers

What is a common cause of autoimmune disorders?

<p>Autoimmune disorders occur when the immune system mistakenly attacks the body's own cells due to a failure in self-recognition.</p> Signup and view all the answers

Briefly describe the function of the variable region of an antibody.

<p>The variable region of an antibody is responsible for binding to specific antigens.</p> Signup and view all the answers

How does increased blood flow contribute to limiting pathogen replication at an infection site?

<p>Increased blood flow raises the temperature at the infection site, which can inhibit the growth and replication of certain pathogens.</p> Signup and view all the answers

Flashcards

Pathogen

Any microorganism that can cause disease, including bacteria, viruses, fungi, and protozoa.

Viruses

Microscopic pathogens that infect host cells and hijack their machinery to reproduce (e.g., HIV).

Bacteria

Single-celled organisms that can cause disease by releasing toxins or damaging tissues (e.g., Mycobacterium tuberculosis).

Protozoans

Single-celled parasites that invade tissues and can cause diseases like malaria (e.g., Plasmodium spp.).

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Skin as a Barrier

The skin serves as a primary physical barrier to pathogens, with features like sebum, exfoliation, and scab formation.

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Blood Clotting

A process that prevents infection by sealing wounds; involves clot formation when skin is broken.

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Phagocytosis

A non-specific response where white blood cells engulf and destroy pathogens.

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Non-Specific Responses

General immune responses that target all pathogens, such as phagocytosis and inflammation.

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Lysosomes

Organelles that digest pathogens in phagocytes.

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Mast Cells

Cells that release histamine to trigger inflammation.

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Histamine Effects

Causes swelling, redness, and heat in response to infection.

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Edward Jenner

Developer of the first smallpox vaccine using cowpox in 1796.

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Non-Specific Immunity

General defenses like skin and phagocytosis against pathogens.

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Specific Immunity

Targets specific pathogens using antibodies and memory cells.

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Antigen

Foreign molecule that triggers an immune response.

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Autoimmune Disorders

When the immune system mistakenly attacks the body's own cells.

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Vaccines

Developed using inactivated, weakened, or genetic material from pathogens to induce immunity.

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Boosters

Additional doses given to reinforce immunity when it decreases over time.

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Active Immunity

Produced by the immune system after infection or vaccination.

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Passive Immunity

Antibodies passed from another source, like mother to baby.

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Natural Immunity

Acquired through natural means, like recovering from disease or maternal transfer.

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Induced Immunity

Gained via medical means such as vaccinations.

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Monoclonal Antibodies

Lab-engineered antibodies that target specific cells, used in treatments.

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Antibiotics

Substances that kill or inhibit bacterial growth, ineffective against viruses.

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Antibiotic Resistance

Resistance developed by bacteria against antibiotics due to misuse or overuse.

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Mechanisms of Resistance

Ways bacteria become resistant, like producing enzymes or modifying target sites.

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Epidemiology

The study of how diseases spread, peak, and decline in populations.

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SIR Model

A model describing disease spread: Susceptible, Infected, Recovered.

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Râ‚€ (Basic Reproduction Number)

The average number of secondary infections from one infected case.

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Public Health Measures in COVID-19

Strategies like lockdowns and social distancing to mitigate spread.

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Flattening the Curve

Reducing infection rates to avoid overwhelming healthcare systems.

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Efficacy of Health Measures

Effectiveness of public health actions during COVID-19 varied by execution.

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Zoonotic Diseases

Diseases that originate in animals and can be transmitted to humans, accounting for 60% of human infectious diseases.

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Rabies

A zoonotic disease caused by a virus, transmitted through bites and leading to severe symptoms and death without treatment.

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Prevention of Zoonotic Diseases

Includes vaccinating pets, avoiding wild animals, and quick wound cleaning to prevent transmission from animals.

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Social Distancing

Keeping space between individuals to reduce virus spread.

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Mask-Wearing

Wearing masks to limit the transmission of airborne diseases.

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Vaccination Campaigns

Efforts to immunize populations to reduce severe disease and death.

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Testing & Contact Tracing

Methods used to identify and isolate disease cases and their contacts.

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Impacts of Lockdowns

Reduced transmission but caused economic and mental health issues.

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Study Notes

Pathogens and Disease

  • A pathogen is any microorganism that causes disease (bacteria, viruses, fungi, protozoa).
  • Pathogens invade the host, multiply, and trigger an immune response.

Causes of Disease

  • Viruses infect host cells and hijack their machinery for reproduction (e.g., HIV).
  • Bacteria release toxins or damage tissues (e.g., Mycobacterium tuberculosis).
  • Protozoans are single-celled parasites that invade tissues (e.g., Plasmodium spp. causing malaria).
  • Fungi cause infections by breaking down tissues (e.g., Candida causing thrush).

Disease Examples

  • AIDS (HIV):
    • Symptoms: Weak immune system, frequent infections, weight loss.
    • Transmission: Bodily fluids (blood, semen, vaginal fluids, breast milk).
    • Treatment: Antiretroviral therapy (ART).
    • Long-term effects: AIDS, increased vulnerability to infections and cancer.
  • Tuberculosis (Mycobacterium tuberculosis):
    • Symptoms: Persistent cough, weight loss, night sweats, fever.
    • Transmission: Airborne droplets.
    • Treatment: Long-term antibiotics (e.g., rifampicin, isoniazid).
    • Long-term effects: Lung damage or spread to other organs.
  • Malaria (Plasmodium spp.):
    • Symptoms: Cyclical fever, chills, sweating, headaches.
    • Transmission: Anopheles mosquito bites.
    • Treatment: Antimalarial drugs (e.g., chloroquine, artemisinin-based therapy).
    • Long-term effects: Anemia, organ damage, or death.
  • Athlete's Foot (Trichophyton):
    • Symptoms: Itchy, flaky skin between toes.
    • Transmission: Contact with infected surfaces.
    • Treatment: Antifungal creams or powders.
    • Long-term effects: Chronic infection if untreated.

General Defense System

  • Skin as a Barrier:
    • Sebum: Oily secretion that inhibits microbial growth.
    • Exfoliation: Constant shedding removes pathogens.
    • Scab formation: Prevents microbial entry after injury.
  • Blood Clotting & Hemophilia:
    • Blood clotting prevents infection by sealing wounds.
    • Hemophilia is a disorder where blood doesn't clot properly, increasing infection risk.

Barriers to Pathogens

  • Physical: Skin, mucus, cilia in the respiratory tract.
  • Chemical: Stomach acid, lysozymes in tears and saliva.
  • Biological: Beneficial gut bacteria outcompeting harmful microbes.

Non-Specific Responses

  • Phagocytosis: White blood cells engulf pathogens.
  • Lysosomes & Lysosomal Enzymes: Break down pathogens inside phagocytes.
  • Mast Cells & Histamine: Trigger inflammation by increasing blood flow and permeability.

Other Important Information

  • Cause of Swelling, Redness, and Heat:
    • Swelling (Edema): Histamine causes fluid leakage from blood vessels.
    • Redness (Erythema): Increased blood flow to the area.
    • Heat: More blood increases temperature, limiting pathogen replication.
  • Edward Jenner's Work: Developed the first smallpox vaccine (using cowpox).
  • Ethical Issues: His research that exposed an 8-year-old without consent is considered unethical today.
  • Differences Between Non-Specific and Specific Immunity:
    • Non-Specific (Innate): General defenses (e.g., skin, phagocytosis, inflammation).
    • Specific (Adaptive): Targets particular pathogens (e.g., antibodies, memory cells).
  • Antigen & Antibody:
    • Antigen: triggers immune response (foreign molecule, usually a protein).
    • Antibody: produced by B cells, binds to specific antigens (Y-shaped protein).
  • Antibody Structure:
    • Constant region: determines antibody class.
    • Variable region: binds to specific antigens.
    • Disulfide bridges: hold the structure together.
  • How Phagocytes Recognize Self and Non-Self: Detect MHC (Major Histocompatibility Complex) markers. Non-self cells have foreign antigens, triggering the process.
  • Autoimmune Disorders:
    • Immune system attacks the body's own cells.
    • Caused by failure in self-recognition.
    • Examples: Type 1 Diabetes, Rheumatoid Arthritis.
  • Humoral vs. Cellular Responses:
    • Humoral: B cells recognize antigens and produce antibodies to neutralize pathogens (extracellular).
    • Cellular: T cells kill infected cells (intracellular).
  • Different Antibody Types (Immunoglobulins): IgG (most abundant, provides long-term immunity, crosses the placenta), IgM (first antibody produced, forms pentamers), and others.
  • Roles of Interleukin-1 (IL-1) and Interleukin-2 (IL-2): IL-1 is secreted to stimulate helper T cells and induce fever (inflammation); IL-2 activates B and T cells for proliferation and expansion.
  • B Cells vs. T Cells: Differences in origin, role, response type, and activation. B cells produce antibodies; T cells destroy infected cells.
  • Roles of Different Immune Cells: B cells (antibodies), Helper T cells (activate B cells, T cells, macrophages), Cytotoxic T cells (destroy infected cells), Memory T cells (long-term immunity), Suppressor T cells (prevent excessive responses).
  • mRNA Vaccines: encode a viral protein for temporary production, allowing the body to build antibodies.
  • Herd Immunity: When a large portion of a population is immune to a disease, reducing its spread.
  • Diseases Outbreaks and Containment: Quarantine & Isolation, Vaccination, Hygiene Measures, Contact Tracing, and Public Health Campaigns.
  • Active vs. Passive Immunity: Acquiring (active) immunity from an infection or vaccine; acquiring (passive) immunity from external sources (e.g., maternal antibodies).
  • Antibiotics: Substances that kill bacteria or inhibit their growth.
  • Antibiotic Resistance: Development through overuse/misuse, mechanisms of bacteria resistance.

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