infectious disease (22-24) Flashcards
(8 cards)
What is the difference between infection and infectious disease? Define the terms pathogenesis and virulence.
Infection is the invasion and multiplication of a microorganism (pathogen) in a host. It may or may not cause harm.
Infectious disease occurs only when that infection leads to damage or dysfunction in the host.
Pathogenesis refers to the biological mechanisms through which an infection leads to disease.
Virulence describes the degree of pathogenicity—in other words, how severe or harmful a pathogen is. Highly virulent pathogens cause more severe symptoms and damage.
Explain the difference between correlation and causality in disease. What are Koch’s postulates and why are they still important today?
Correlation: Two things happen together but don’t necessarily cause one another.
Causality: One thing directly causes another (e.g., a microbe causes a disease).
Koch’s Postulates are four criteria to determine if a microorganism causes a disease:
It must be found in all individuals with the disease, but not in healthy ones.
It must be isolated and grown in pure culture.
When introduced into a healthy host, it must reproduce the disease.
It must be re-isolated from the newly infected host and match the original.
Define virulence factors. Give examples and explain how they help microbes harm the host.
Virulence factors are molecules produced by pathogens that enhance their ability to cause disease.
These can:
Damage host cells directly,
Evade immune responses,
Facilitate spread through tissue.
🔬 Examples:
Exotoxins – e.g., Cholera toxin (AB5) from V. cholerae increases cAMP → ion imbalance → severe diarrhea.
Exoenzymes – e.g., Collagenase from Clostridium perfringens breaks down connective tissue (gas gangrene).
Endotoxins – e.g., LPS from Gram-negative bacteria triggers dangerous inflammation (fever, shock).
Adhesins & Pili – e.g., N. gonorrhoeae Type IV pili helps bacteria attach and evade immune attack through antigenic variation.
Compare the innate and adaptive immune systems in terms of speed, specificity, and memory.
Innate immunity is your body’s first line of defense. It kicks in immediately, within minutes to hours. It’s non-specific, meaning it responds the same way to any invader. Innate immunity has no memory, so it doesn’t improve after repeated exposure. Its main components include physical barriers (like skin), phagocytes, natural killer (NK) cells, and complement proteins.
Adaptive immunity, on the other hand, is your specialized and elite defense system. It responds more slowly at first — taking days — but it’s highly specific to each unique antigen (invader). Most importantly, it has long-lasting memory, meaning it remembers past infections and responds faster the next time. Its components include B cells, T cells, and antibodies.
Give specific examples of innate and adaptive immune defenses and explain their roles in protecting the host.
nnate Immunity:
Skin & Mucus – physical barriers.
Phagocytes (macrophages, neutrophils) – engulf pathogens.
Complement System – triggers lysis, opsonization, and inflammation.
Natural Killer Cells – kill infected cells without prior exposure.
🧠 Adaptive Immunity:
B cells – produce specific antibodies.
T cells:
Helper T cells (CD4+): coordinate response.
Cytotoxic T cells (CD8+): kill infected cells.
Memory Cells – enable quicker response to future infections.
Describe the strategies microbes use to evade immune detection and destruction.
Immune Evasion Strategies:
Antigenic variation – e.g., N. gonorrhoeae changes surface pili proteins.
Inhibition of phagocytosis – capsule-forming bacteria like S. pneumoniae.
Complement interference – some pathogens block complement activation.
Molecular mimicry – mimic host molecules (e.g., Treponema pallidum).
Latency & hiding inside cells – e.g., HIV integrates into host genome.
How has scientific research helped improve strategies for controlling infectious diseases?
Vaccination – Eradicated smallpox; mRNA platforms emerged for COVID.
Drug development – e.g., ART for HIV, ACTs for malaria.
Genetic sequencing – Identifies pathogens, tracks mutations, informs treatment.
Diagnostics – Rapid tests and PCR allow early detection.
Public health – Research shapes policies on hygiene, quarantine, vector control.
Identify current global challenges in infectious disease control, with named examples.
Key Challenges:
Antimicrobial resistance (AMR): MDR-TB is rising, and resistance in malaria is emerging.
No vaccine for HIV due to rapid mutation and immune evasion.
Socioeconomic inequality: Poorer regions lack access to vaccines, treatment, and information.
Misinformation: Vaccine hesitancy affects herd immunity.
Global health crises: COVID-19 disrupted malaria control programs, leading to resurgences.
🌍 Named examples:
HIV: 39.9M living with it in 2023; two-thirds in Sub-Saharan Africa.
Malaria: 263M cases in 2023; >75% deaths in children under 5.
TB: 10.8M active cases, 1.25M deaths, with 400K MDR-TB cases.
