topic 2 infectious disease

What is a pathogen?

A biological agent ( virus, bacteria, fungus) that causes disease or illness

What is a vector?

An organism that carries and transmits a pathogen to another host

What is the difference between an epidemic and a pandemic?

An epidemic is more cases than expected in a region; a pandemic has spread across multiple countries/continents

Why are prions hard for the immune system to detect?

They are mutated proteins with no DNA/RNA, so they don't trigger an immune response

Why are viruses considered non-living?

They cannot reproduce without hijacking a host cell's machinery

What are the 5 syllabus modes of disease transmission?

Direct contact, body fluids, contaminated food, contaminated water, vectors

What do capsules do as a virulence factor?

Protect the pathogen from the host's immune system

What do toxins do as a virulence factor?

Are proteins that damage host tissue

In the antibiotic disk diffusion practical, what does a larger zone of inhibition mean?

The antibiotic is more effective against that bacteria

What does 'no zone of inhibition' indicate?

The bacteria are resistant to that antibiotic

What are the three lines of defence in vertebrates?

1st: physical/chemical barriers (non-specific); 2nd: inflammatory response and complement system (non-specific); 3rd: adaptive immune response (specific)

What is the role of MHC markers?

They act as an identity tag so the immune system recognises self from non-self

What causes vasodilation in the inflammatory response?

Prostaglandins and histamine released by damaged cells

What is the difference between neutrophils and macrophages?

Neutrophils arrive first and perform phagocytosis; macrophages also phagocytose and present antigens to activate other immune cells

How do natural killer cells destroy infected/cancer cells?

Using perforin and granzymes to trigger apoptosis, without needing prior activation

Where do B lymphocytes mature, and what do they respond to?

Mature in the bone marrow; respond to pathogens/toxins outside cells

Where do T lymphocytes mature, and what do they respond to?

Mature in the thymus gland; respond to infected cells, cancer cells, and transplanted tissue

What is the role of Helper T cells?

Recognise antigens, activate B cells and other T cells - the key signalling cell for the immune response

What is the role of Regulator T cells?

Turn off the immune response once the antigen is gone

What are the four ways antibodies work?

Neutralisation, agglutination, precipitation, complement activation

What is naturally acquired active immunity?

Catching a disease and the body producing its own antibodies in response

What is artificially acquired passive immunity?

Preformed antibodies injected into the body, e.g. antivenom

What is herd immunity?

When enough of a population is vaccinated/immune, protecting those who cannot be vaccinated

What physical defences do plants use against pathogens?

Bark, thorns, cell walls, leaf hairs, waxy cuticle

What are plant defensins?

Proteins that inhibit fungi, bacteria and viruses

Why does soap remove pathogens more effectively than water alone?

Soap dissolves the oily film pathogens stick to on skin, washing them away

What is contact tracing?

Identifying and notifying people who have been near an infected person so they can quarantine

Name the 4 factors affecting the spread of disease.

Pathogen persistence, transmission mechanism, population immunity, mobility of individuals

What does a point source outbreak look like in the data?

A single sharp peak, suggesting everyone was exposed to the same source at once

What does a propagated outbreak look like in the data?

Multiple peaks over time, suggesting person-to-person spread