Infection as a mechanism of disease

Question 1

What is infection?

Answer 1

• colonisation of a host by microbial species
• infecting microbes seek to use host’s resources to reproduce, often resulting in disease
• caused by micro-organisms like viruses, prions, bacteria and viroids
• macro parasites and fungi can also infect.

Question 2

How is infection classified?

Answer 2

They are classified by the causative agent as well as by the constellation of symptoms and medical signs produced.

Question 3

What is an apparent infection?

Answer 3

An infection that produces symptoms

Question 4

What is a latent infection?

Answer 4

An infection that is inactive/dormant

Question 5

What is a silent/subclinical/apparent infection?

Answer 5

An infection that is active but does not produce noticeable symptoms.

Question 6

What is an exogenously acquired infection?

Answer 6

From bacteria in the environment e.g. food, water, air, insect bites, animals

Question 7

What is an endogenously acquired infection?

Answer 7

Caused by agents on or in us e.g. alteration of microbiome, injuries introducing skin bacteria (e.g. staphylococci).

Question 8

What conditions are required for infection to spread from one person to another?

Answer 8

1) One person must be infected with a micro-organism
2) The other person must be susceptible to infection with that micro-organism
3) The micro-organism must be able to leave the body of the infected person and enter the body of the susceptible person

Question 9

What is colonization?

Answer 9

• infection present on surface of the body
• organism propagating at a rate sufficient to maintain its numbers without producing identifiable evidence of any reaction in host.

Question 10

What is an inapparent/subclinical infection?

Answer 10

• organism not only multiplying but also causes a measurable reaction that is however not clinically detectable.

Question 11

What is a symptomatic infection?

Answer 11

organism causes clinically detectable reaction

Question 12

What is an opportunistic infection?

Answer 12

infection arises in individuals with compromised immunity - may be caused by micro-organisms that are commonly found in the host’s environment or flora.

Question 13

What is the latency period?

Answer 13

the time between infection agent and onset of infectiousness

Question 14

What is the incubation period?

Answer 14

The time between infection and onset of symptoms

Question 15

What is disease?

Answer 15

Any deviation from a condition of good health and well-being

Question 16

What is infectious disease?

Answer 16

A disease condition caused by the presence or growth of infectious micro-organisms or parasites

Question 17

What is pathogenicity?

Answer 17

• The ability of a microbe to cause disease (often used to describe or compare species)

Question 18

What is virulence?

Answer 18

• The degree of pathogenicity in a micro-organism (used to describe or compare stains within a species)

Question 19

What is acute infection?

Answer 19

An infection characterised by sudden onset, rapid progression, and often with severe symptoms

Question 20

What is chronic infection?

Answer 20

An infection characterised by delayed onset and slow progression

Question 21

What is primary infection?

Answer 21

An infection that develops in an otherwise healthy individual

Question 22

What is secondary infection?

Answer 22

An infection that develops in an individual who is already infected with a different pathogen

Question 23

What is localised infection?

Answer 23

An infection that is restricted to a specific location or region within the body of the host

Question 24

What is a systemic infection?

Answer 24

An infection that has spread to several regions or areas in the body of the host.

Question 25

What does the suffix "-emia" mean?

Answer 25

presence of an infectious agent e.g. bacteremia - presence of infectious bacteria

Question 26

What does the suffix "-itis" mean?

Answer 26

inflammation of.... e.g. endocarditis - inflammation of the heart chambers

Question 27

What is epidemiology?

Answer 27

The study of the transmission of disease

Question 28

What is a communicable disease?

Answer 28

A disease that can be transmitted from one individual to another

Question 29

What is a contagious disease?

Answer 29

A communicable disease that is easily spread from one individual to another

Question 30

What is a non communicable disease?

Answer 30

A disease that is not transmitted from one individual to another

Question 31

What is an endemic disease?

Answer 31

A disease condition that is normally found in a certain percentage of a population

Question 32

What is an epidemic disease?

Answer 32

A disease condition present in a greater than usual percentage of a specific population

Question 33

What is a pandemic disease?

Answer 33

An epidemic affecting a large geographical area; often on a global scale

Question 34

What is a reservoir of infection?

Answer 34

The source of an infectious agent

Question 35

What is a carrier?

Answer 35

An individual who carries an infectious agent without manifesting symptoms, yet who can transmit the agent to another individual

Question 36

What is a fomite?

Answer 36

Any inanimate object capable of being an intermediate in the indirect transmission of an infectious agent

Question 37

What is an animal vector?

Answer 37

An animal (non human) that can transmit an infectious agent to humans

Question 38

What is a biological animal vector?

Answer 38

The infectious agent must incubate in the animal host as part of the agents development cycle e.g. transmission of malaria by infected mosquitoes

Question 39

What is a mechanical animal vector?

Answer 39

The infectious agent is physically transmitted by the animal vector, but the agent does not incubate or grow in the animal e.g. bacteria transmission via sticking to the feet of flies.

Question 40

What is mutualism?

Answer 40

A symbiotic relationship in which both species benefit.

Question 41

What is commensalism?

Answer 41

A symbiotic relationship in which one species benefits, and the other species is neither helped nor harmed

Question 42

What is parasitism?

Answer 42

A symbiotic relationship in which one species benefits, and the other species is harmed. Generally, the species that benefits (the parasite) is much smaller than the species that is harmed (the host).

Question 43

Where is normal flora present?

Answer 43

1) Skin 2) Upper respiratory tract 3) Oral cavity 4) Intestine, especially large intestine 5) Vaginal tract

Question 44

Where is flora NOT present?

Answer 44

1) Lower respiratory tract 2) Muscle tissue 3) Blood and tissue fluid 4) Cerebrospinal fluid 5) Peritoneum 6) Pericardium 7) Meninges

Question 45

Where is there little normal flora?

Answer 45

Eyes and stomach

Question 46

What are the benefits of the normal flora?

Answer 46

1) Nutrient production/processing 2) Competition with pathogenic microbes 3) Normal development of the immune system