infection - infection prevention

Question 1

what are the communicable nature of infections?

Answer 1

from non-human source to human

person to person: direct / indirect (vector - malaria)

Question 2

what are the consequences of transmission?

Answer 2

endemic disease: usual background rate

outbreak: 2+ cases linked in time & place
epidemic: infection rate greater than usual background (endemic)
pandemic: V high rate of infection across many regions (countries & continents)

Question 3

what is the basic reproduction number?

Answer 3

R0 - the average number of cases 1 case generates over the course of its INFECTIOUS period in an otherwise uninfected, NON-immune population (ebola)

Question 4

what does R0 > 1, R0=1, R0 <1 mean?

Answer 4

R0 > 1 = increase in case
R0 = 1: stable case number
R0 < 1 = decrease in case

Question 5

what are the reasons for outbreaks, epidemics, pandemics?

Answer 5

4 P’s:
new pathogen: antigens, virulence factors, antibacterial resistance
patient: (new host) non-immunes, healthcare effects
new practice: social, healthcare e.g. introduce surgery
place

Question 6

what are the factors determining the transmissibility?

Answer 6

1. infectious dose: no. of microorganisms required to cause infection (e.coli - low infectious dose, salmonella & cholera - high infectious dose required)
2. varies by: micro-organism, presentation of micro-organism, immunity of potential host

Question 7

what do epidemic curves show?

Answer 7

number of people infected at each time interval?

susceptible –> infected –> recovered

Question 8

what are the interventions of the 4 P’s which can prevent infections?

Answer 8

Pathogen: reduction / eradication (disinfectants, decontamination, sterilisation)

patient: improved health (nutrition, medical treatment), immunity (passive materal, active vaccine)
practice: behavioural change e.g. hand-washing, safe sex, food preparation, PPE
place: environmental, engineering (safe water, air, good housing, space between hospital beds)

Question 9

good consequences of control?

Answer 9

decreased incidence / elimination of disease e.g. smallpox, polio

Question 10

bad consequences of control of infection?

Answer 10

decreased exposure to pathogen –> decreased immune stimulus –> decreased antibody –> increased susceptibles –> outbreak
later average age of exposure –> increased severity e.g. Hep A, chicken pox, rubella