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Infection > Session 8: Preventing Infections > Flashcards

Session 8: Preventing Infections Flashcards

1
Q

Give examples of how transmissible infections can transmit.

A

From a non-human source to humans (common source) From person to person directly From person to person indirectly via a vector

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2
Q

Give example of common sources of transmission of infection.

A

Environmental source Food/water Animals

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3
Q

Give an example of an environmental source.

A

Legionella pneumophila

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4
Q

Give an example of a food/water source

A

Salmonella Salmonella typhoid is also transmissible from person to person

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5
Q

Give an example of an animal source

A

This is also called zoonotic and rabies is one.

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6
Q

Give examples of direct transmission from person to person.

A

Influenza Norovirus (winter vomiting disease) Neisseria gonorrhoea HIV Chlamydia

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7
Q

Give examples of indirect transmission from person to person.

A

Malaria with the help of mosquitos.

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8
Q

Define endemic disease.

A

Usual background rate of disease

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9
Q

Define outbreak.

A

Two or more cases of a single disease and single strain of that disease in time and place.

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10
Q

Define epidemic.

A

A rate of infection greater than the usual background rate. Epidemic > Endemic

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11
Q

Define pandemic.

A

A very high rate of infection spreading across many regions, countries and continents.

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12
Q

Define basic reproduction number (R0).

A

The average number of cases one case generates over the course of its infectious period, in an otherwise uninfected, non-immune population.

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13
Q

What does R0 > 1 mean?

A

That there is an increase in cases. One case generates more than an additional case. It is not linear.

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14
Q

What does R0 = 1 mean?

A

A stable number of cases.

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15
Q

What does R0 < 1 mean?

A

There is a decrease in cases.

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16
Q

Give examples of diseases with a high R0 vs. low R0.

A

High: measles (12-18), pertussis (12-17) Low: Sars (2-5), Influenza (2-3)

17
Q

Give reasons for outbreaks, epidemics and pandemics.

A

A new pathogen An old pathogen with new antigens. New hosts New practice

18
Q

How could an old pathogen get new antigens?

A

There are two main sorts: Antigenic shift and antigenic drift.

19
Q

Explain antigenic shift.

A

If a person has two strains of influenza (e.g.) at the same time you might end up with a new novel strain of influenza which can spread. It is rare but it can happen. This is a fast change.

20
Q

Explain antigenic drift.

A

Mutation of the pathogen. This is a slow change.

21
Q

What is more detrimental? Antigenic shift or antigenic drift?

A

Antigenic shift is more hazardous because it is a fast change and it means that everyone will be susceptible. Like the swine-flu. This causes a higher susceptibility to outbreak, epidemic and pandemic. In the case of antigenic drift it is a slow progression of change which means there is less susceptibility.

22
Q

Explain how a new host could cause outbreak.

A

A new host like babies after the antibodies from the mother disappeared or in immunosuppressed which receive bone marrow transplants they won’t have any native immune system ready to act. This can cause new outbreaks.

23
Q

Explain how a new practice could cause outbreak.

A

A social change like in 1980s San Francisco where homosexuality became accepted. A paradigm shift where gay sex became more common lead to an increase in HIV transmission. Health care changes like blood products (transfusions) where money was an incentive to make people donate blood. Mostly IVDUs started donating blood in order to get more money for their addiction. Since there was no screening of HIV at the time this lead to even more transmission of HIV among people.

24
Q

Define infectious dose. Give factors influencing infectious dose.

A

Number of micro-organisms required to cause an infection. Varies by: Microorganism Presentation of microorganism Immunity of potential host E.g. Salmonella has a high infectious dose over 10^5 of organisms needed to cause an infection. E. coli has a low infectious dose where less than 10 organisms needed to cause infection.

25
Q

Give examples of epidemic curves.

A

Bell-shaped.

Cyclical like norovirus.

Stochastic nature of small scale outbreaks

26
Q

Expain epidemic curve of stochastic nature.

A

Appears random where the epidemic might be small, it might be short, and it might come and go at varied intervals.

27
Q

How can you intervene pathogen infection?

A

The pathogen itself.

Patient

Practice

Place

28
Q

Explain pathogen intervention.

A

Reduction or eradication of the pathogen in form of antibacterial and disinfectants, decontamination and sterilisation.

Reduction and eradication of vector by eliminating vector breeding sites.

29
Q

Patient intervention of infection.

A

Improved health:
Nutrition
Medical treatment

Immunity:
Passive like maternal antibodies, intravenous immunoglobulin
Active like vaccination

30
Q

Explain herd immunity.

A

Vaccination of a sufficient proportion of a population is enough to not only protect the vaccinated but also the other people who are not vaccinated.

31
Q

Practice intervention of infection.

A

Avoidance of pathogen or its vector:
Geographically (don’t go to that place)
Protective clothing, equipment like long sleeves, trousers against mosquito bites. Personal protective equipment in hospitals like gowns, gloves and masks.

Behavioural:
Safe sex
Safe disposal of sharps
Food and drink preparation

32
Q

Place intervention of infection.

A

Environmental engineering like:

Safe water
Safe air
Good quality housing
Well designed healthcare facilities

33
Q

What are the good consequences of control of infection?

A

Decreased incidence or elimination of disease like small pox, polio (almost) and dracunculiasis.

34
Q

What are the bad consequences of prevention of infection?

A

Decreased exposure to pathogen -> decreased immune stimulus > decreased antibody > increased susceptibles > outbreak.

Later average age of exposure can lead to increased severity like:

Polio
Hep A
Chicken Pox
Congenital Rubella Syndrome

35
Q
A

Infection (17 decks)

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