Disease

What is an infectious disease?

A disease caused by a pathogen that can be transmitted between organisms.

What is a non-infectious disease?

A disease that is not caused by a pathogen and generally cannot be transmitted between people.

Main difference between infectious and non-infectious diseases

Infectious diseases are caused by pathogens and can be transmitted; non-infectious diseases are not caused by pathogens and generally cannot be transmitted.

What is a pathogen?

An organism or infectious agent capable of causing disease.

What are the five major types of pathogens?

Bacteria, fungi, viruses, prions and parasites.

What are bacteria?

Single-celled microorganisms. Some cause disease by damaging cells or producing toxins.

Give examples of bacterial diseases.

Tuberculosis and cholera.

What are fungi?

Organisms such as yeasts and moulds. Some cause infectious diseases.

Give examples of fungal diseases.

Ringworm and athlete's foot.

What are viruses?

Very small infectious agents that reproduce inside host cells.

Give examples of viral diseases.

Influenza, measles and COVID-19.

What are prions?

Misfolded proteins that can cause other proteins to misfold, particularly in the nervous system.

Give an example of a prion disease.

Creutzfeldt-Jakob disease (CJD).

What are parasites?

Organisms that live in or on a host and obtain resources from the host.

Give examples of parasitic diseases.

Malaria and tapeworm infections.

What is transmission?

The process by which a pathogen spreads from one host to another.

What is airborne/respiratory transmission?

The spread of pathogens through infectious droplets or particles released when an infected person breathes, coughs, sneezes or talks.

What is direct contact transmission?

The spread of a pathogen through physical contact with an infected person.

What is indirect contact transmission?

The spread of a pathogen through contaminated objects or surfaces.

How can food and water transmit disease?

Pathogens can enter the body when contaminated food or water is consumed.

How can blood transmit disease?

Pathogens can be transmitted through infected blood or certain body fluids.

What is vector transmission?

The transmission of a pathogen by another organism, such as a mosquito.

Give an example of vector transmission.

Mosquitoes can transmit malaria parasites.

What is mother-to-child transmission?

The transmission of a pathogen from a mother to her child during pregnancy, birth or breastfeeding.

What is the first line of defence?

Physical and chemical barriers that prevent pathogens from entering the body.

Examples of the first line of defence

Skin, mucus, cilia, tears, saliva and stomach acid.

How does the skin defend against pathogens?

It forms a physical barrier that prevents many pathogens from entering the body.

How does mucus defend against pathogens?

It traps pathogens and particles.

What do cilia do?

They move mucus and trapped pathogens out of the respiratory system.

How does stomach acid defend against pathogens?

Its low pH destroys or damages many pathogens that are swallowed.

What is the second line of defence?

A non-specific immune response that attacks pathogens that have entered the body.

What does non-specific mean?

The defence acts against many different types of pathogens rather than targeting one specific pathogen.

What are phagocytes?

White blood cells that engulf and destroy pathogens.

What is phagocytosis?

The process where a cell surrounds, engulfs and destroys a pathogen or foreign particle.

What is inflammation?

A response to infection or tissue damage involving increased blood flow and immune activity.

What is a fever?

An increase in body temperature that can help the body fight some infections.

What is the third line of defence?

A specific immune response that targets particular pathogens or antigens.

What are lymphocytes?

White blood cells involved in the specific immune response.

What are B cells?

Lymphocytes that can produce antibodies.

What is an antibody?

A protein produced by B cells that specifically binds to a particular antigen.

What is an antigen?

A molecule or marker recognised by the immune system, often found on a pathogen.

Antigen vs antibody

An antigen is the target recognised by the immune system; an antibody is a protein that specifically binds to that target.

What are memory cells?

Immune cells that remain after an infection and allow a faster response if the same pathogen is encountered again.

Why are memory cells important?

They allow the immune system to respond faster and more strongly to a previously encountered pathogen.

What is vaccination?

The introduction of a safe form or component of a pathogen to stimulate an immune response and create immune memory.

How does vaccination work?

A vaccine exposes the immune system to an antigen, causing antibodies and memory cells to develop.

Why can vaccination protect against future infection?

Memory cells allow the immune system to recognise the pathogen and produce a faster, stronger response.

What is an antibiotic?

A medicine used to treat certain bacterial infections.

Do antibiotics kill viruses?

No. Antibiotics target bacterial structures or processes and do not kill viruses.

Why don't antibiotics work against viruses?

Viruses do not have the bacterial structures or processes targeted by antibiotics.

What is antibiotic resistance?

The ability of bacteria to survive antibiotics that would normally kill them or stop their growth.

How does antibiotic resistance develop?

Susceptible bacteria are killed while resistant bacteria survive, reproduce and become more common through natural selection.

How can antibiotic resistance be reduced?

Use antibiotics only when appropriate, follow instructions and do not use antibiotics for viral infections.

How can infectious diseases be reduced?

Vaccination, hand hygiene, sanitation, safe food and water, isolation, appropriate treatment and vector control can reduce transmission.

How can non-infectious diseases be reduced?

Healthy diet, regular physical activity, avoiding smoking, sun protection and appropriate health checks can reduce risk.

What is an epidemic?

An occurrence where disease cases rise above what is normally expected in a population or region.

What is an endemic disease?

A disease that is consistently present in a particular population or geographical area.

What is a pandemic?

An epidemic that spreads across multiple countries or continents and affects large numbers of people.

Endemic vs epidemic

Endemic means a disease is normally present in an area; epidemic means cases are above the expected level.

Epidemic vs pandemic

An epidemic is an unusually high occurrence in a population or region; a pandemic has widespread international or global spread.