Lecture 3

Question 1

Define prion

Answer 1

Unusual infectious agents which appear to only consist of protein without any genetic material

Question 2

Define viruses

Answer 2

Very small intracellular parasites that require a living host for replication

Question 3

Define bacteria

Answer 3

Unicellular organisms that do not require living tissue to survive

Question 4

Define Fungi

Answer 4

Single to multi-cellular, diverse range of yeasts and moulds

Question 5

Define parasite

Answer 5

An organism that lives on or in a host, at the expense of the host (a non-mutual relationship)

Question 6

Name and explain the three types of parasites

Answer 6

Protozoa - unicellular organisms with no cell wall

Helminths - multi-cellular organisms (worms)

Arthropods - insects

Question 7

Name the 5 modes of transmission

Answer 7

Contact, airborne, water-borne, food borne, vector (transmission by a carrier)

Question 8

4 potential sources of infection

Answer 8

1. Socioeconomic factors (eg. hygiene), 2. nosocomial (originating in a hospital), 3. Iatrogenic (caused by medical examination or treatment). 4. Zeoonotic (exposure to animals).

Question 9

Name 4 portals of entry for microbes

Answer 9

Skin (e.g mucosal surfaces, ears, lacrimal glands, puncture wounds), Respiratory tract (e.g. inhaled aerosols/spores or droplets), GIT (eg. contaminated food/water), Genitourinary system (e.g. urethra - contaminated from faecal route, STD, urinary retention).

Question 10

Name 7 portals of exit for microbes

Answer 10

Sputum and mucosal secretions, saliva, semen and vaginal secretions, urine, faeces, blood.

Question 11

Name five stages of infection

Answer 11

Incubation, prodromal illness, acute/invasive phase, decline, convalescence.

Question 12

What is the incubation period?

Answer 12

The time interval between exposure of the infectious agent and the onset of symptoms of infection.

Question 13

What is the incubation period of food posioning?

Answer 13

12-36 hours

Question 14

What is the incubation period of tuberculosis?

Answer 14

4-12 weeks

Question 15

What is the incubation period of influenza?

Answer 15

2-3 days

Question 16

What is the prodromal period?

Answer 16

The onset of disease symptoms, signals the beginning of the disease. As the pathogen multiplies, non-specific disease symptoms emerge such as headache, nausea, general malaise.

Question 17

What is the acute/invasive stage?

Answer 17

Period of acute disease (specific signs and symptoms relative to the disease are observed). Pathogen invades and damages host tissue.

Question 18

What are characteristics of the acute/invasive stage?

Answer 18

Fever and chills caused by the release of pyrogens.

Question 19

What symptoms may emerge during the prodomal period?

Answer 19

Headache, nausea, general malaise (non specific disease symptoms).

Question 20

What are the two outcomes of infection?

Answer 20

Recovery or death

Depends on the ability of the host to overcome the invasive phase

Question 21

What is the decline phase?

Answer 21

The immune system overcomes the effects of the pathogens and symptoms subside, and patient begins to recover.

Question 22

What is the convalescence phase?

Answer 22

The time when the body repairs itself and regains strength.

Question 23

What are the signs of infection?

Answer 23

Inflammation, pain or tenderness, swelling, redness, warmth, purulent exudate-bacterial, serous exudate - viral.

Question 24

What are the symptoms of infection?

Answer 24

Fever, fatigue, weakness, headache, nausea, skin rashes