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IMED2001 UWA > Lecture 3 transmission of infection and principles of disease > Flashcards

Lecture 3 transmission of infection and principles of disease Flashcards

1
Q

Where are the portals of exit?

A

identical to entry

Exiting can be through coughing, sneezing, saliva, sputum

Pathogens also leave via blood, vaginal secretions, semen, urine, and faeces

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2
Q

Pregnant women and babies infection note:

A

Unique interactions between mother and the foetus

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3
Q

What affects spread of infection?

A

Reservoirs (places where pathogens grow and accumulate)

Mechanisms of transmission (ways pathogens move)

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4
Q

What are some potential reservoirs for pathogens?

A

Humans

Other animals

Non-living reservoirs such as water food and soil

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5
Q

How can humans and other animals be as reservoirs?

A

Sick people show symptomsa and are easy to identify but difficult when symptoms are yet to develop or have ceased

Carriers of infection can transmit disease but show no symptoms

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6
Q

How can non-living reservoirs move disease around?

A

Water is a necessity and can hold pathogens

Leading to high levels of faecal contamination in water can lead to infections spreading via faecal oral route

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7
Q

How can infection be spread?

A

Contact

Vehicle

Vector

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8
Q

What are the types of contact transmission?

A

Direct (touching)

Indirect (touching something someone else touched)

Droplets (airborne)

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9
Q

What is a commonly touched item that causes infectious disease transmission called?

A

A fomite

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10
Q

What are some pathogens transmitted through direct contact?

A

Staph

Hep A

Smallpox

STIs

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11
Q

What are some examples of indirect contact transmission?

A

Sharing of needles HIV

Snotty tissue transmission

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12
Q

What pathogens are often transmitted by droplets?

A

Influenza and whooping cough

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13
Q

What factors are important to droplet transmission?

A

Distance (short distance more likely to transmit)

Size (large droplets fall to the ground quickly smaller droplets stay airborne for a while)

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14
Q

What is vehicle transmission?

A

Can involve pathogens riding along on air food water and this enters body and transmits infection

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15
Q

How is air used as a vehicle?

A

Spores can float in air

Dust can use air as a vehicle containing huge numbers of pathogens

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16
Q

What is vector transmission?

A

using an organism as an intermediary such as an insect which carries infection

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17
Q

What are the types of vector transmission?

A

Mechanical (pathogens on vector’s body passively brushed off onto host)

Biological (pathogens are within vector transmission through bite)

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18
Q

What are some vector organisms?

A

Fleas

Ticks

flies

mosquitos

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19
Q

Do pathogens use vector to replicate?

A

Some pathogens multiply in vector and arrive at new host lin larger numbers making establishment of infection more likely (less virulent pathogens still establish infection as a result)

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20
Q

What are zoonotic disease?

A

diseases that require an animal intermediary.

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21
Q

How are zoonotic diseases typically transferred?

A

Usually through direct contact with humans but can be through indirect contact as well as is the case with waste material of litter box, fur, feathers, infected materials, etc

It can also be transmitted by vectors from animals to humans

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22
Q

What are 3 methods to control transmission of diseases?

A

Isolation

Quarantine

Vector control

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23
Q

How is isolation typically carried out?

A

Prevent infected individuals from contact with general population

7 categories of isolation

Patients usually are isolated in hospital

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24
Q

What are the limitations of isolation?

A

Don’t always know when individual is infected such as

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25
How is quarantine carried out?
Separate those exposed from the population Quarantine should last as long as incubation period of disease Once symptoms subside quarantine is lifted
26
What are the limitations of quarantine?
Very difficult to enforce.
27
How is vector control carried out?
Killing vectors or using repellants Mosquito nets
28
What is the difference between vector and vehicle transmission?
Vector transmission is generally living organism Vehicle is non-living
29
Difference between indirect transmission and vehicle transmission:
Time between pathogen landing on intermediate item and it being transmitted. Sometimes categories overlap
30
What factors affect disease transmission?
Age Gender Lifestyle Occupation Emotional state Climate
31
How does age affect disease transmission?
Disease levels tend to increase with age
32
How does gender affect disease transmission?
Some more prevalent in one gender than others
33
How does lifestyle affect disease transmission?
poor nutrition can decrease immuno-competence in host
34
How does occupation affect disease transmission?
More infections in health care workers
35
How does emotional state affect disease transmission?
vulnerable emotional state can decrease immune competence in host
36
How does climate affect disease transmission?
Greater incidence of respiratory illness in colder climates
37
What is immunocompetence?
Ability of host to mount defence
38
What happens if host defences are compromised?
Potential for infectious diseases increases
39
Which group of people are more vulnerable to infections?
People with AIDS or genetic insufficiency diseases People doing chemo Surgical transplant and burn patients Premature newborns Elderly Patients on artificial ventilators with cannulas and catheters
40
What is neutropenia?
Lower neutrophil numbers in blood.
41
What are neutrophils?
Form of primary phagocytic defence and important component of innate immune system
42
What are the most common causes of profound neutropenia?
Administration of cytotoxic chemotherapy Cancer of other diseases with damaged bone marrow Congenital disorders with poor bone marrow function Viral infections Autoimmune disorders that destroy bone marrow cells Overwhelming infections that use neutrophils faster than they can be made
43
What kind of infections take advantage of neutropenia?
Bacterial and fungal infections Often associated with surgical procedures and catheterisation
44
Why are transplant recipients immunocompromised?
Immunity is lowered to prevent rejection of the organ.
45
How are infections treated in organ transplat patients?
Broad spectrum antibiotics
46
Why are burn victims more immunocompromised?
Loss of large areas of primary physical barrier results in greater chance of infection
47
What bacteria is most problematic for burn patients?
Pseudomonas aeruginosa
48
Where can opportunistic pathogens arise from?
Normal flora in our bodies
49
How can opportunistic infections arise?
Movement of opportunistic organisms from one area to another where It can be pathogenic as is the case with UTIs and in cases where flora is compromised by antibiotics
50
What are nosocomial infections?
hospital infections and are usually associated with intravenous applications
51
What must hospitals consider regarding nosocomial infections?
Source of infection Mode of transmission Susceptibility of patient to infection Prevention and control
52
What are the most common sites of the sites of nosocomial infections?
Urinary tract Respiratory tract Surgical wounds
53
What are the most common sources of infections within hospital environment?
Other patients Hospital staff Visitors Unsanitary conditions Water supplies Respiratory equipment Catheters
54
What are the most common pathogens in nosocomial infections?
E. Coli Enterococcus species Staph (+MRSA and VRSA) Clostridium difficile Pseudomonas aeruginosa Many are antibiotic resistant
55
What are the measures put in place to prevent spread of disease in hospitals?
PPE Washing hands with antiseptic before and after Cleaning spills of blood or contaminated fluids
56
What must hospital programs address regarding nosocomial infections?
Surveillance of nosocomial infections On-site microbiology lab and standard isolation procedures Standardised procedures for use of catheters and hospital equipment Proper decontamination and sanitary procedures Mandatory nosocomial-disease education programs Infection-control specialist on staff
57
What is the difference between incidence and prevalence?
Incidence is the number of new cases Prevalence is the total number of people infected within a specific population at any given times (Prevalence is always a larger number because some people will not be newly infected at that given time)
58
What is the difference between morbidity and mortality?
Morbidity refers to the number of individuals affected by the disease Mortality is the number of deaths
59
What is the morbidity rate?
Number of people affected during a set period divided by total population
60
What is mortality rate?
Number of people died due to specific disease during a set period of time divided by total population
61
How do epidemiological studies classify diseases?
Sporadic (occurring in random manner) Endemic (disease constantly in population in low numbers) Epidemic (incidence of disease suddenly higher than expected morbidity and mortality rates may increase and could eventually become a worldwide problem) Pandemic (worldwide epidemic)
62
What is a common source epidemic?
Arises from contact with contaminated substance that affects large number of people and subsides quickly when contamination dealt with (eg. listeria in rockmelon)
63
What is a propagated epidemic?
Epidemic that is amplified by person to person contact and remains in population for a long time and is more difficult to deal with that common source outbreak
64
What is herd immunology?
When majority of population is immune there are few potential hosts and disease essentially disappears. (This is why vaccines are so effective)
65
What are notifiable diseases?
Diseases that must be reported to the health department of local and state governments.
66
Why are urinary nosocomial infections most common?
Due to catheters
67
What is the aetiology of a disease?
Cause of a disease
68
How can a disease be proven to be a disease? | How can a microorganism be said to cause a disease?
Koch's postulates
69
What happens with cultures that cant be grown in pure culture?
Syphilis (treponema pallidum) Mycobacterium leprae (leprosy) Viruses and rickettsial organisms
70
What are the 5 stages of a disease?
Incubation period (no signs or symptoms) Prodromal period (vague general symptoms) Illness (most severe signs and symptoms) Decline (declining signs and symptoms Convalescence (no signs and symptoms)
71
How long is the incubation?
Incubation period varies with virulence of pathogen
72
What is a possible problem that could arise after decline?
Secondary infections
73
What are some non-communicable diseases?
CVD Stroke diabetes etc
74
What is the difference between communicable and contagious?
Communicable refers to diseases that can potentially be transmitted and if they are easily spread they are said to be contagious
75
What are the 4 categories of disease duration?
Acute (develops quickly lasts short time) Chronic (develops slowly lasts long tim) Sub-acute (insidious onset (6 - 12 months) almost always fatal Latent (remains in host after symptoms disappear can come back years later)
76
What does duration of disease depend on?
Overall health of the host
77
What are persistent bacterial infections?
Pathogenic bacteria capable of maintaining infections in hosts even in presence of inflammatory specific antimicrobial mechanisms and a good immune response.
78
How are persistent bacterial infections treated?
Specific anti-microbial therapy
79
What is the scope of an infection?
scope is whether infection is localized (contained/walled off) Systemic (moved away from starting point)
80
What is bacteraemia?
Bacteria in blood
81
What is septicaemia?
Bacteria growing in blood
82
What is toxaemia?
Toxins in blood
83
What is viraemia?
Viruses in blood
84
What are the 3 types of infection?
Primary (initial infection has acute onset of symptoms) Subclinical (No symptoms visible and are carriers) Secondary (People weakened from primary infection and ill again)
85
What is toxic shock?
Massive leakage of plasma from circulatory system causing massive drop in BP.
86
What causes toxic shock?
Neutrophils come in contact with M proteins on bacterial surface
87
What percentage of people that are affected by toxic shock die?
It is fatal for 30 - 70% of patients
88
What is sepsis?
Presence of pathogen/toxin in blood
89
What are the 2 forms of sepsis?
severe and acute
90
What is severe sepsis?
Sytemic inflammation and organ dysfunction Causes abnormal temperature, HR, Respiratory rate, and WBC count Elevated number of liver enzymes Kills slowly over period of weeks with minimal tissue inflammation or damage
91
What is acute septic shock?
Sudden onset causes death in 24-48 hours Widespread tissue inflammation and cell damage

IMED2001 UWA (44 decks)

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