Post on 27-Mar-2015
Introduction to Public Health Surveillance
Dr Giri Shankar
Lazareto de Mahon, Menorca, Spain24 September –12 October 2012
&
&
2
Surveillance Track
6 Lectures; 2 case studies
Mon 24 Sept – Introduction to PH surveillance
Tue 25 Sept – Event based surveillance
Wed 26 Sept
•Key elements of a surveillance system ( I & II)
•Analysis of surveillance data
Fri 28 Sept – Evaluation of surveillance system
&
3
Outline of Lecture
Definition of Surveillance
Surveillance Loop
Uses of Surveillance with examples
Summary
&
What is Surveillance?
4
The systematic process of collection, transmission, analysis and feedback of public health data for
decision making
Could you drive without looking at the traffic?
Can you make public health decisions in the absence of
data?
&
5
“The continued watchfulness over the distribution and trends in the incidence of
disease through the systematic collection, consolidation and evaluation of morbidity
and mortality reports and other relevant data”
Alexander Langmuir, Chief Epidemiologist, CDC
“Continuous analysis, interpretation and feedback of systematically collected data,
generally using methods distinguished by their practicality, uniformity and rapidity,
rather than by accuracy and completeness”
WJ Eylenbosch & ND Noah (eds). Surveillance in Health and Disease. Oxford University Press 1988.
”The systematic ongoing collection, collation and analysis of data for public health
purposes and the timely dissemination of public health information for assessment
and public health response as necessary.”
World Health Assembly 2005
Definitions of surveillance
&
6
Surveillance is
Information for action
&
7
The surveillance loop
Health care system
Surveillance centre
Reporting
Feedback, recommendations
An
alysis, in
terpretation
Event
Action
Data
Information
Planning, Evaluation, Policy formulation
Source: S Hahne, S Cotter, D Werker - EPIET
8
Event and population under surveillance
Population and time
• Everyone in the country or region
• Patients in hospitals
• Employees in a factory
• All children in the winter months
Event
Disease
SyndromeAcute flaccid paralysisInfluenza-like illnessDiarrhoea
Infection
Public health issue
Antimicrobial resistance
EnvironmentVector populationWater quality
&
&
9
The surveillance loop
Health care system
Surveillance centre
Reporting
Feedback, recommendations
An
alysis, in
terpretation
Event
Action
Data
Information
Planning, Evaluation, Policy formulation
Source: S Hahne, S Cotter, D Werker - EPIET
&
10
Surveillance methods- key data items collected
Numerators
number of cases of disease
antibody positive samples
number of resistant strains
Descriptors
characteristics of patients, strains etc
Denominators
total population at risk (or sub-sample) in a given time frame
total number of strains examined
11
Case definition&
YES
A case is an event
An event is something that happens to:
A person,
In a given place,
At a given time
A case definition is a set of criteria that triggers reporting
NO
A case is not a person
Events do not exist if you lack info:
On the person
On the place
On the onset date
A case definition is not a diagnosis made to decide treatment
12
Case definition
Includes:
• Time, place, person
• Clinical features
and /or
• Laboratory results
and/or
• Epidemiological features
Should be:
• Clear, simple
Field tested
• Stable and valid
&
Possible caseClinical diagnosis of meningitis or septicaemia or other invasive disease where the CCDC/CPH, in consultation with the clinician and microbiologist, considers that diagnoses other than meningococcal disease are at least as likely
Probable caseClinical diagnosis of meningitis or septicaemia or other invasive disease where the CCDC/CPH, in consultation with the physician and microbiologist, considers that meningococcal infection is the most likely diagnosis
Confirmed caseClinical diagnosis of meningitis, septicaemia or other invasive diseaseAND at least one of:• Neisseria meningitidis isolated from normally sterile site• Gram negative diplococci in normally sterile site• Meningococcal DNA in normally sterile site• Meningococcal antigen in blood, CSF or urine. 13
&Case definition
14
Reporting (data transfer)
Data transfer method
• Paper by mail• Telephone• E-mail• Secure Internet
Data transfer frequency
• For every case• Daily• Weekly• Quartery
Individual data
• Identified – name, personal id number
• Non-identified – but possible to trace back
• Anonymous – impossible to trace back
Aggregated data• Numbers
• Tabulated numbers – by sex, age group etc
&
&
15
The surveillance loop
Health care system
Surveillance centre
Reporting
Feedback, recommendations
An
alysis, in
terpretation
Event
Action
Data
Information
Planning, Evaluation, Policy formulation
Source: S Hahne, S Cotter, D Werker - EPIET
&
16
Surveillance data sources
Generic sources
Notifications of infectious diseases
Microbiology laboratory reports
Hospital Episode Statistics
Primary Care spotter practices
Screening programmes (antenatal, blood donors)
Prescriptions / over the counter drug sales
&
17
Surveillance data sources
Disease or patient specific sources
Customised surveillance programmes
∙ voluntary e.g. HIV/AIDS surveillance
∙ mandatory e.g. Clostridium difficile
∙ enhanced e.g. meningococcal disease
Patient registers e.g. renal registry
Clinical networks e.g. British Paediatric Surveillance Unit (BPSU)
Non health sources
Veterinary medicine domestic & wild animals, animal husbandry
Environment health water, food, air sampling
Population statistics e.g. death registrations
&
18
The surveillance loop
Health care system
Surveillance centre
Reporting
Feedback, recommendations
An
alysis, in
terpretation
Event
Action
Data
Information
Planning, Evaluation, Policy formulation
Source: S Hahne, S Cotter, D Werker - EPIET
&
19
Analysis of surveillance dataDescriptive use
Measure of disease frequency
incidence (no. cases/population at risk over given time period) e.g. 5 cases per 1000 person years; 0.3 cases per 1000 bed-days
prevalence (no. cases/population at risk at a set time) e.g. 15% of patients sampled antibody positive; 3% strains erythromycin resistant
Data described according to time-person-place
Analytical use
Comparison between groups to gain a measure of increased risk
e.g. case fatality in males vs females
e.g. change in rate of infection over time
&
20
Surveillance is
Information for action
21
Purposes and uses of surveillance
• describe the disease and its importance
• monitor secular trends
• detection of outbreaks & emerging epidemics
• monitor health practices
• monitor changes in infectious agents
• provide an evidence base for policy and guidance formulation
• monitor control and prevention measures
• generate hypotheses and stimulate public health research
what is the problem?
how do we deal with it?
did it work?
how can we do better?
&
&
22
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents • provide an evidence base for policy and guidance formulation• monitor control and prevention measures• generate hypotheses and stimulate public health research
&
23
Notifications of Meningococcal Infections
Cases of group B and C meningococcal disease in England and Wales, by age group -1998-2004
&
24
Purposes and uses of surveillance
• describe the disease and its importance
• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents • provide an evidence base for policy and guidance formulation• monitor control and prevention measures• generate hypotheses and stimulat public health research
25
TB notification and death rate England and Wales, 1913 - 2000 &
&
26
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends
• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents • provide an evidence base for policy and guidance formulation• monitor control and prevention measures• generate hypotheses and stimulate public health research
27
UK epidemiology: containment phaseRCGP weekly ILI rate 2009/10 and recent years.
0
50
100
150
200
250
19-Apr 31-May 12-Jul 23-Aug 04-Oct 15-Nov 27-Dec 07-Feb 21-Mar
ILI r
ate
per 1
00 0
00
Week-ending date
2008/09 2007/081999/2000 2009/10Baseline* Epidemic threshold*
First UK cases detected
* Baseline activity<30 per 100,000; epidemic activity>200 per 100,000
28
Age and sex distribution of confirmed H1N1v cases in the UK, 30 June 2009
(n= 6766)(FluZone) &
29
Regional Spread of cases - May
10 May 31 May
&
30
Regional spread of cases - June
05 June12 June
19 June26 June
&
31
UK epidemiology: treatment phase
RCGP weekly ILI rate 2009/10 and recent years, England
0
50
100
150
200
250
19-Apr 31-May 12-Jul 23-Aug 04-Oct 15-Nov 27-Dec 07-Feb 21-Mar
ILI r
ate
per 1
00 0
00
Week-ending date
2008/09 2007/081999/2000 2009/10Baseline* Epidemic threshold*
First UK cases detected
Switch to 'treatmentonly' phase
* Baseline activity<30 per 100,000; epidemic activity>200 per 100,000
&
32
UK epidemiology: launch of National Pandemic Flu Service
RCGP weekly ILI rate 2008/09 and recent years, England
0
50
100
150
200
250
19-Apr 31-May 12-Jul 23-Aug 04-Oct 15-Nov 27-Dec 07-Feb 21-Mar
ILI r
ate
per 1
00 0
00
Week-ending date
2008/09 2007/081999/2000 2009/10Baseline* Epidemic threshold*
First UK cases detected
Switch to 'treatmentonly' phase
NPFS Launched and Schools close for summer
* Baseline activity<30 per 100,000; epidemic activity>200 per 100,000
&
33
UK epidemiology: end of first wave
RCGP weekly ILI rate 2009/10 and recent years.
0
50
100
150
200
250
19-Apr 31-May 12-Jul 23-Aug 04-Oct 15-Nov 27-Dec 07-Feb 21-Mar
ILI r
ate
per 1
00 0
00
Week-ending date
2008/09 2007/081999/2000 2009/10Baseline* Epidemic threshold*
First UK cases detected
Switch to 'treatmentonly' phase
NPFS Launched and Schools close for summer
schools re-open
* Baseline activity<30 per 100,000; epidemic activity>200 per 100,000
&
34
UK epidemiology: end of first wave
RCGP weekly ILI rate 2009/10 and recent years.
* Baseline activity<30 per 100,000; epidemic activity>200 per 100,000
0
50
100
150
200
250
19-Apr 31-May 12-Jul 23-Aug 04-Oct 15-Nov 27-Dec 07-Feb 21-Mar
ILI r
ate
per 1
00 0
00
Week-ending date
2008/09 2007/081999/2000 2009/10Baseline* Epidemic threshold*
First UK cases detected
Switch to 'treatmentonly' phase
NPFS Launched and Schools close for summer
schools re-open
Schoolhalf-term break
&&
&
35
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics
• monitor health practices
• monitor changes in infectious agents • provide an evidence base for policy and guidance formulation• monitor control and prevention measures• generate hypotheses and stimulate public health research
&
36
Distribution of surgical site infection by category of surgical procedure
Oct 1997 - Dec 2003
0
5
10
15
20
25
% o
pe
ratio
ns
infe
cte
d
&
37
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices
• monitor changes in infectious agents
• provide an evidence base for policy and guidance formulation• monitor control and prevention measures• generate hypotheses and stimulate public health research
38
Staphylococcus aureus bacteraemia reports and methicillin susceptibility England & Wales
&
&
39
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents
• provide an evidence base for policy and guidance formulation
• monitor control and prevention measures• generate hypotheses and stimulate public health research
&
40
Number of new HIV diagnoses¹ by prevention group², UK: 1999-2008
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Ne
w H
IV d
iag
no
ses
MSM
Heterosexual contact in the UK
Heterosexual contact abroad
IDU
Blood product recipients
Mother-to-child transmission
¹ Numbers will rise as further reports are received, particularly for recent years² Adjustments made for missing information relating to patient exposure
MESH Department - Centre for Infections
&
41
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents • provide an evidence base for policy and guidance formulation
• monitor control and prevention measures• generate hypotheses and stimulate public health research
42
Laboratory confirmed serogroup C meningococcal disease
end of catch-up
start of routine immunisation and catch up (15-17y, <1y)
Source: Meningococcal Reference Unit/CfI
&
&
43
Cumulative reports of Pneumococcal Disease due to the seven serotypes IN Prevenar™ : Children < 2 Years in E&W by Epidemiological Year
&
44
Cumulative reports of Pneumococcal Disease due to the seven serotypes NOT in Prevenar™ : Children < 2 Years in E&W by Epidemiological Year
&
45
Purposes and uses of surveillance
• describe the disease and its importance• monitor secular trends• detection of outbreaks & emerging epidemics• monitor health practices • monitor changes in infectious agents • provide an evidence base for policy and guidance formulation• monitor control and prevention measures
• generate hypotheses and stimulate public health research
&
46
MRSA bacteraemia in children
proposal to undertake enhanced surveillance of MRSA in children
&
47
Summary
Surveillance is a lively line of communication that works
both ways
A surveillance system counts the same events,
consistently, every day
Surveillance directs decision-making
&
48
Surveillance is
Information for action
Remember