Communicable disease Flashcards
What to include when describing disease cases/ admissions graph
Background rates
Rising rates
Rates that remain same
If 2 sets of data, compare
Possible explanations for rising disease rates
Outbreak of infectious disease
Seasonal variation
Artefactual: Change in reporting habits, increased vigilance
Random variation
Strengths of passive surveillance systems
Good for common disease
Cheaper as it uses existing data
Useful background trend data
Can provide early warning
Cons of passive surveillance systems
Completeness requires motivation to report
Dependant on reporting timescales from health centres
Accuracy including vulnerability to responder bias
Data available is limited to what is collected
Inappropriate for rare or severe diseases
What is a reservoir
An animal, environmental or person where the pathogen exists
Define an outbreak
2 or more cases that are linked
Occurrence of a disease not expected in the area
What is a common source outbreak
When a group of persons have been exposed to a common source of an infectious agent (restaurant, class, shop)
What is a point source outbreak
When the exposure to an infectious agent/ toxin has occurred over a brief period of time
What is a propagated outbreak
When an outbreak is gradually spreading from person to person
Define endemic
If there is a persistent level of infectious disease in an area
Define hypr-endemic
If there is persistently high levels occurrence of disease occurrence in an area
Define sporadic
Describes the situation where there is a random or irregular pattern of disease occurrence
Define epidemic
When a disease outbreak occurrence within an area is in excess of what is expected for a given time period
Define pandemic
When an epidemic becomes widespread and affects several countries for example
What is the infectious
The quantity of micro-organisms needed to produce infection in the host
Define incidnece
Number of NEW cases of a disease occurring over a given time period in a defined populaiton at risk
What is cumulative incidence
Total number of NEW cases of a disease occurring over a time period
For example, if 1,500 cases of cholera occurred in a district (population 100,000) over a 1
month period, the cumulative Incidence would be 1.5%
What is the incidence rate
measures disease frequency by calculating new cases per unit of person-time at risk. It accounts for varying observation periods and changing populations, making it more precise than crude incidence. Formula: (New cases) ÷ (Total person-time at risk)
Define attack rates
Attack rate measures the proportion of a defined population that develops a disease during a limited outbreak period. It’s calculated as (new cases ÷ total population at risk) × 100%.
Define surveillance
Systematic and ongoing collection of data. It makes use of already available data that is routinely collected.
What is the purpose of surveillance
Detect any change in disease trends
Gather timely feedback for action
Name 3 things surveillance can be ‘carried out’ on
Occurrence of particular disease
Determinants of a disease
Animal and bird reservoirs
What does surveillance enable us to do
Detection of any change in a disease
Tracking of changes in a disease
Detection of new diseases
Monitoring and evaluation of preventive and control measures
Prioritisation of decisions
What are the key components of an effective data surveillance system
Occurrence of health related event
Event reported by sources
Data management
Dissemination of information
Public health action
