Week 1 Intro to Immune System

Question 1

Endemic Disease

Answer 1

disease is ALWAYS present in a population within a region

Question 2

Epidemic:

Answer 2

a rapid increase in cases higher than expected in a population within a region, e.g. SARS, Ebola, Cholera

Question 3

Pandemic

Answer 3

An epidemic that becomes widespread over several regions, countries, or continents e.g. COVID

Question 4

Chain of Infection

Answer 4

Reservoir – habitat in which the organism normally lives, grows, and multiplies. There can be human reservoirs, animal reservoirs or environmental reservoirs

Portal of Exit – The portal of a pathogens tend to be the same as portals of entry (or where they tend to be localized) – pathogens often leave hosts in materials the body secretes/excretes

Mode of Transmissions: physical, vehicle, airborne, droplets, vector

Portal of Entry – The portal of entry refers to the manner in which a pathogen enters a susceptible host. The portal of entry must provide access to tissues in which the pathogen can multiply or a toxin can act.

Host Susceptibility - The final link in the chain of infection is a susceptible host. Susceptibility of a host depends on genetic or constitutional factors, specific immunity, and nonspecific factors that affect an individual’s ability to resist infection or to limit pathogenicity.

Question 5

Modes of Transmission

Answer 5

• Physical contact – direct person to person contact, whether skin to skin, kissing, or sexual intercourse ie) STIs, cold sores, HPV
• Vehicle borne - is where the pathogen is transmitted from source to susceptible host via intermediate object (fomites), as well as food and water
• Airborne - occurs when infectious agents are carried by dust or droplet nuclei suspended in air, which can sometimes by for a long time and can be blown over large distances
• Droplets – large spray with short-range aerosols produced by sneezing coughing or even talking etc which are sprayed only a few feet before dropping to the ground
• Vector borne – animal or insect

Question 6

Transmission may be interrupted when:

Answer 6

Infectious agent is eliminated, inactivated, or cannot survive in the reservoir (identification, cleaning)

Exit managed (hand hygiene, PPE, waste disposal)

Transmission prevented (hand hygiene, isolation, air control)

Entry protected (aseptic technique, catheter care)

Patient susceptibility reduced (treat underlying disease, identify high-risk patients)

Question 7

Host-Pathogen Relationship: Dependent on 3 main factors

Answer 7

• Number of organisms in or on the host – higher the number higher the risk
• Virulence of the organism – capacity of a pathogen to cause disease
• Host defenses or degree of resistance

Question 8

Why do some pathogens cause disease and others don’t?

Answer 8

• Virulence! The ability of an organism to cause infectious disease
• Some infectious agents are easily transmitted (very contagious), but they are not very likely to cause disease (not very virulent)
• Other infectious agents are very virulent but not terribly contagious, e.g. Ebola

Question 9

Virulence Factors of Pathogen: Flagella

Answer 9

protein-like structure that helps to move around

Question 10

Virulence Factors of Pathogen : Pili

Answer 10

aka ambrae – short filament around cell wall to help bind the cell or grab hold of them + infect them = adherence factor

Question 11

Virulence Factors of Pathogen : Capsules

Answer 11

protective walls – make macrophages and neutrophils unable to phagocyte them

Question 12

Virulence Factors of Pathogen : endospores

Answer 12

heat + cold resistance, resistance to drying in chemical agents – making it difficult to destroy them

Question 13

Virulence Factors of Pathogen : Biofilms

Answer 13

bunker that is impermeable to our host antibody reaction

Question 14

Virulence Factors of Pathogen: Exotoxins

Answer 14

Exotoxins – are proteins that are released by bacteria to cause disease manifestation

Neurotoxins act on nerves + motor endplates to cause paralysis

Enterotoxins act on GI tract to cause diarrhea by inhibiting NaCl reabsorption + killing intestinal epithelial cells – resulting in a massive osmotic pull of fluids into the intestine that causes diarrhea

Pyrogenic exotoxins stimulate the release of cytokines that can cause rashes + fevers

Tissue invasion exotoxins destroy and tunnel through our dermatological tissues

Question 15

Virulence Factors of Pathogen : Endotoxins

Answer 15

Endotoxins- are lipopolysaccharide A and are found mostly on gram-negative bacteria – responsible for causing host effects such as fever, changes in BP, inflammation and, lethal shock, + other toxic events

Question 16

Host Susceptibility

Answer 16

• Immune system
• Age
• Nutrition
• Genetic disorders
• Medications (e.g. chemo)

Question 17

Host Resistance

Answer 17

prevent infectious disease from occurring and developing
Barriers - functional epithelial layer
Chemical – tears, saliva, gastric juices
Immunity against a particular agent