epidemiology in practice

Question 1

passive surveillance

Answer 1

based on reports from health care workers

Question 2

active surveillance

Answer 2

all cases are reported by a system that is set up for this reason

Question 3

sentinel surveillance

Answer 3

we look for trends in disease in certain sites instead of covering whole population

Question 4

what influences spread of disease

Answer 4

properties of agent, sources of infection, biological reservoirs, host factors, exposure variation, environment

Question 5

infectivity

Answer 5

ability of an organism to invade and multiply in a host

Question 6

methods of transmission

Answer 6

direct (touching or inhaling secretions), indirect (vehicle), airborne (droplet nuclei)

Question 7

development of disease

Answer 7

Infection, Incubation (latent –> infectious period), Clinical disease (infectious period), Recovery

Question 8

epidemic

Answer 8

unexpected increase in incidence of disease in one area/group

Question 9

endemic

Answer 9

constant presence of disease or infectious agent within a geographical area of population group

Question 10

pandemic

Answer 10

unexpected increase in incidence of disease that cross international boundaries

Question 11

cluster

Answer 11

greater aggregation of relatively uncommon events or disease in space and or time that are thought to be greater than due to chance

Question 12

primary case

Answer 12

1st person infected

Question 13

index case

Answer 13

the first person recognised by health authorities that makes them aware an outbreak is occurring

Question 14

2nd generation

Answer 14

next people infected from primary case

Question 15

secondary attack rate

Answer 15

how many people the primary infects

Question 16

common source

Answer 16

when everyone gets outcome from same common source e.g. Arana serving dodgy chicken once. Epidemic curve has triangular shape

Question 17

continuous source

Answer 17

continuous exposure e.g. local well infected with virus. Epidemic curve has long flat shape

Question 18

intermittent source

Answer 18

repeated common common source e.g. arana serving dodgy chicken 3 times a week

Question 19

propagated source

Answer 19

one person spreads it to another etc

Question 20

mixed source

Answer 20

starts as common source then develops into propagated source

Question 21

what is screening

Answer 21

widespread use of a simple test for a disease in an apparently healthy (asymptomatic) population

Question 22

what is a screening programme

Answer 22

organised system using a screening test among asymptomatic people in the population to identify early cases of disease in order to improve outcomes

Question 23

what is a screening test

Answer 23

a test, usually relatively cheap and simple, used to test large numbers of apparently healthy people to identify individuals suspected of having early disease who will then go on to have further diagnostic tests to confirm the diagnosis

Question 24

lead time

Answer 24

time from when disease is detectable and when symptoms appear

Question 25

criteria for screening

Answer 25

disease is chronic and serious, has high prevalence, long lead time, can improve length or quality of life, change course of disease

Question 26

what is sensitivity

Answer 26

• Proportion of people with the disease who test positive
• true positive/(all with disease)
• Test specific
• High = good

Question 27

what is specificity

Answer 27

• Proportion of people without the disease who test negative
• True negative/(all without disease)
• Test specific
• High = good

Question 28

what is tradeoff between sensitivity and specificity

Answer 28

have to Consider consequences of missing cases (false negatives) versus false alarms (false positives).

if disease is severe then should maximise sensitivity.

if test expensive then should maximise specificity