Infection Prevention

Question 1

Many infections are transmissible and common sources may be found that lead to a lot of cases. Please give some examples of non-human to human infection sources.

Answer 1

Environment - Legionella pneumophilia (no onwards transmission).
Food/wate - food poisoning organisms with inwards transmission possible.
Animals - rabies, with possible onwards transmission.

Question 2

Give some examples of direct and in-direct person to person acquired infections.

Answer 2

Direct: Influenza Norovirus, Neisseria gonorrhea.

Indirect person to person requires a vector: female mosquitos and malaria.

Question 3

What are the 4 possible consequences of transmission?

Answer 3

Endemic, outbreak, epidemic or pandemic.

Question 4

What’s the difference between endemic and epidemic?

Answer 4

If a disease is endemic, it’s just at its usual background rate, whereas if there’s an epidemic, the rate of infection is greater than the usual endemic rate.

Question 5

What constitutes an outbreak of an infection?

Answer 5

Two or more cases linked in time and place, plausibly connected.

Question 6

What does it mean if there is a disease pandemic?

Answer 6

A very high rate of infection spreading across many regions, countries or continents, often by novel microorganisms.

Question 7

Define the Basic Reproductive Number - R0. What can be told from it?

Answer 7

The average number of cases one case generates over the course of its infectious period, in an otherwise unaffected, non-immune population.
If R0<1–> decrease in cases, R0>1–> increase in cases or R0=1–> there’s a stable number of cases.

Question 8

The 4Ps of infection prevention can help explain reasons for outbreaks, epidemics and pandemics. How is this so for ‘pathogen’?

Answer 8

A new pathogen - antigens (antigenic drift/shift), virulence factors and antibacterial resistance may cause an outbreak.

Question 9

The 4Ps of infection prevention can help explain reasons for outbreaks, epidemics and pandemics. What about patients explains outbreaks?

Answer 9

New hosts/patients, may be non-immune and have healthcare effects.

Question 10

New practises, socially and healthcare wise may lead to infection outbreaks, but how is place connected?

Answer 10

Place may encompass, the pathogen, patient and practise.

Question 11

One factor determining transmissibility if an infection, is the infectious dose. Explain.

Answer 11

The infectious dose is the number of microorganisms required to cause infection, which varies by microorganism, as well as its presentation and the immunity of the potential host.

Question 12

Epidemic curves are ______ shaped and show the number of people ___________ at different time intervals. People go from being susceptible, to infected, then ___________. An example is Norovirus outbreak reports, with peaks corresponding to _________ months.

Answer 12

Bell
Infected
Recovered
Winter

Question 13

In which case will outbreaks not show the normal epidemic curve?

Answer 13

The stochastic nature of small scale outbreaks mean that they may not show the normal epidemic curve, as can be explained by probability and chance.

Question 14

How can pathogens be interfered with to prevent outbreaks?

Answer 14

Pathogens (+/- vector) may be reduced or eradicated with antibacterials, including disinfectants. There’s also decontamination, sterilisation and elimination of vector breeding sites.

Question 15

What patient interventions may occur to prevent infections?

Answer 15

Improve health (nutrition, medical treatment) and immunity - passive e.g. Maternal antibodies, IV immunoglobulins or active via vaccination.

Question 16

Herd immunity provides indirect protection for those not ____________. The proportion of the population that needs to be vaccinated depends on the R0 (________ ____________ __________).

Answer 16

Vaccinated

Basic reproductive number

Question 17

What interventions can occur with practice, to prevent infections?

Answer 17

Avoidance of a pathogen/its vector, geographically or with protective clothing/equipment (long sleeves and trousers for mosquito bites or personal protective equipment in hospitals-gowns, gloves and masks). Also behavioural interventions, such as safe sex, appropriate disposal of sharps, food and drink preparation.

Question 18

What about a place can benefit from an intervention, in terms of infection prevention?

Answer 18

Environmental engineering: safe water and air, good quality housing and well designed healthcare facilities.

Question 19

Infection prevention control requires multi-disciplinary skills - ‘from genes to latrines’ and surveillance is important. List some good and bad consequences of infection control.

Answer 19

Good: decreased incidence/elimination of a disease/organism (e.g. Smallpox, polio, guinea worm).
Bad: decrease exposure to a pathogen means decreased immune stimulus and so decreased antibodies, meaning increased susceptibilities, which could lead to an outbreak or later age of exposure, which can result in increased severity (Polio, Hep A, chicken pox, congenital rubella syndrome).