Download What is surveillance?

Introduction to
Public Health Surveillance
Tunisia, 28th October 2014
Dr Gordana Kuzmanovska
National Public Health Institute,
The former Yugoslav Republic of Macedonia
[email protected]
Learning Objectives
•
What is surveillance?
•
Public health/epidemiological surveillance
•
Purposes and uses of public health surveillance
•
Data sources
•
Components of public health surveillance
•
Types of surveillance
What is surveillance?
Could you drive without looking at the traffic?
Can you make public health
decisions in the absence of data?
Definition
”Surveillance is the ongoing process of
systematic collection, collation, analysis and
interpretation of data; than dissemination of
information to those who need to know
(feedback ) in order that action may be taken”
World Health Assembly 2005 (modificated)
Surveillance is information
for action!
“Good surveillance does not necessarily
ensure the making of the right decisions,
BUT it reduces the chances of
[making the] wrong ones.”
Alex Langmuir, 1963
Purposes of public health surveillance
• Assess public health status
• Define public health priorities
• Evaluate existing programs
• Trigger public health action
• Stimulate research
Surveillance objectives
Surveillance should be SMART...
S - Specific (regarding event which is subject of )
M - Measurable (gain info for comparison )
A - Action oriented (information for action)
R - Realistic & (feasible in time and place)
T - Timely (action implemented in time to be effective)
Setting objectives – balance between requirements and
interests!
Characteristics (attributes) of
surveillance system
•
•
•
•
•
•
•
•
Simplicity
Flexibility
Acceptability
Sensitivity
Positive predictive value
Representativeness
Timeliness
Usefulness
Uses of public health surveillance
•
•
•
•
•
•
•
Detection of sudden changes in disease occurrence
and distribution
Monitoring trends and patterns
Detection of changes in health practices
Monitoring changes in infectious agents
Evaluation of control measures
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
Surveillance components
The surveillance loop
Health care
system
Surveillance
centre
Data
Event
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Reporting
Event and population under Surveillance
EVENT
• Disease
• Syndrome
– Acute flaccid paralysis
– Influenza-like illness
– Diarrhoea
• Infection
POPULATION AND TIME
• Everyone – country, region, city
• Patients in hospitals
• Employees in a factory
• Public health issue
– Antimicrobial resistance
• Environment
– Vector population
– Water quality
• All children in the winter
months?
The surveillance loop
Health care
system
Reporting
Data
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Event
Surveillance
centre
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 in a given time frame
– total number of strains examined
– or sub-sample
Case definition
YES
 NO
- A “case” is an event
- A “case” is not a person
- An event is something that
happens to:
- Events do not exist if you
lack info:
•
A person,
o On the person
•
In a given place,
o On the place
•
At a given time
o On the onset date
- A case definition is a set of
criteria that triggers
reporting
- A case definition is not a
diagnosis made to decide
treatment
Case definition (ii)
Includes:
Should be:
Time, place, person.
Clear, simple
Clinical features
Field tested
and /or
Laboratory results
and/or
Epidemiological features
Stable and valid
Adopted
Case definition (iii)
Meningococcal disease (SURVEILLANCE PURPOSES)
Possible case
Clinical 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 case
Clinical 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 case
Clinical diagnosis of meningitis, septicaemia or other invasive disease
AND 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.
Case definition (iv)
Ebola case-classification criteria
(OUTBREAK INVESTIGATION)
Suspected (possible) case
Any person, alive or dead, who has (or had) sudden onset of high fever and
had contact with a suspected, probable or confirmed Ebola case, or a dead
or sick animal OR any person with sudden onset of high fever and at least
three of the following symptoms: headache, vomiting, anorexia/loss of
appetite, diarrhea, lethargy, stomach pain, aching muscles or joints,
difficulty swallowing, breathing difficulties, or hiccup; or any person with
unexplained bleeding OR any sudden, unexplained death.
Probable case
Any suspected case evaluated by a clinician OR any person who died from
‘suspected’ Ebola and had an epidemiological link to a confirmed case but
was not tested and did not have laboratory confirmation of the disease.
Confirmed case
A probable or suspected case is classified as confirmed when a sample from
that person tests positive for Ebola virus in the laboratory.
Reporting (data transfer)
• Data transfer method
– Paper by post
– Telephone
– E-mail
– Secure Internet (web based)
• Data transfer frequency
– For every case
– Daily
– Weekly
– Quarterly
Reporting (data transfer)
• 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.
The surveillance loop
Health care
system
Surveillance
centre
Event
Data
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Reporting
Data Sources
•
•
•
•
•
•
•
•
Notifications of infectious diseases
Microbiology laboratory reports
Sentinel surveillance
Hospital records / primary health care records
Registries
Screening programmes (antenatal, blood donors)
Prescriptions / over the counter drug sales
Surveys
Non medical data sources:
•
•
•
•
Populacion statistics (vital statistic records-birth registration)
Veterinary surveillance, Vectors (Wild and domestic animals
Environmental (food, water, air sampling)
Media (internet, newspapers, TV)
The surveillance loop
Health care
system
Surveillance
centre
Data
Event
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Reporting
Analysis of surveillance data
Data analyzing according to time-place-person!
Descriptive use
Measures of disease frequency:
• Incidence: no. cases/population at risk over given time
period
– 5 cases per 1000 person years; 0.3 cases per 1000 bed-days
• Prevalence : no. cases/population at risk at a set time
– 15% of patients sampled antibody positive;
– 3% strains erythromycin resistant
Analysis of surveillance data (ii)
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
• Analytic methods
Time-series analyses to detect aberrations
Time-space clustering
Interpretation:
What accounts for increased cases?
•
•
•
•
•
•
•
•
Changes in reporting procedure or surveillance system
Changes in case definition
Improvements in diagnostic procedures / new lab testing
Improved access to health care
Increased awareness (doctors), health seeking behavior
(patients)
Changed circumstances - new physician/new clinic –
may see more referred cases, make diagnosis more often,
report more consistently, more responsible
Laboratory or diagnostic error
OR
A true increase in incidence
Figure 5.7 Reported Cases of
Salmonellosis per 100,000 Population,
By Year — United States, 1972–2002
Figure 5.8 Reported Cases of AIDS,
by Year — United States* and U.S.
Territories, 1982–2002
Source: Centers for Disease Control and Prevention.
Summary of notifiable diseases–United States, 2002.
Published April 30, 2004, for MMWR 2002;51(No. 53): p.
59.
•Total number of AIDS cases includes all cases reported to
CDC as of December 31, 2002. Total includes cases among
residents in the U.S. territories and 94 cases among persons
with unknown state of residence.
Source: Centers for Disease Conrol and Prevention.
Summary of notifiable diseases–United States, 2002.
Published April 30, 2004, for MMWR 2002;51(No. 53): p.
59.
The surveillance loop
Health care
system
Surveillance
centre
Event
Data
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Reporting
Dissemination of Surveillance Data
• Dissemination should be “Up and Down”
– Surveillance summaries / reports
– Health agency newsletter (Epi Bulletin)
– Medical / epidemiologic journal articles
– Press releases (web)
The surveillance loop
Health care
system
Surveillance
centre
Event
Data
Planning, Evaluation,
Policy formulation
Action
Information
Feedback,
recommendations
Analysis,
interpretation
Reporting
Surveillance is information
for action!
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution (outbreaks & emerging epidemics)
Monitor trends and patterns
Detect changes in health practices
Monitor changes in infectious agents
Evaluate control measures
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
Reported diarrhea cases by week,
East Amman, Jordan 1995-2000
Can you see an outbreak of disease?
Reported diarrhoea cases by week,
East Amman, Jordan 1995-2000 (ii)
Here it is the outbreak!
Registered influenza cases in R. of Macedonia in
the epidemic years 2009-2010, by weeks
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution
Monitor trends and patterns, prediction of
outbreak
Detect changes in health practices
Monitor changes in infectious agents
Evaluate control measures
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
Registered HIV/AIDS cases and deaths in the
former Yugoslav Republic of Macedonia, by
years (1989-2013)
30
Cases
25
Deaths
20
15
10
5
0
HIV+ tested TB patients received CPT and ART,
2003-2010
Source: World Health Organisation. Collaborative TB/HIV activities, 2010
Estimated number of adults and children
living with HIV in former Yugoslav Republic of
Macedonia by 2015
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution
Monitor trends and patterns
Detect changes in health practices/monitoring
progress
Monitor changes in infectious agents
Evaluate control measures
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
ile
B
A
bd
om
liv
er
ia
lh
ys
or
te
C
pa
or
re
on
nc
ct
om
re
ar
at
y
y
A
ic
rte
su
ry
rg
B
er
yp
y
as
s
G
G
as
ra
To
tri
ft
c
ta
su
lh
rg
ip
er
re
y
H
p
ip
la
ce
he
m
m
en
ia
t
rth
K
r
op
ne
la
e
st
re
y
La
pl
ac
rg
em
e
bo
en
w
t
el
s
Li
O
ur
m
pe
ge
b
n
ry
a
re
m
du
pu
ct
ta
io
tio
n
n
S
of
m
f
al
ra
lb
ct
ur
ow
e
el
su
V
as
rg
cu
er
y
la
rs
ur
ge
ry
du
ct
,
Distribution of surgical site infection by category
of surgical procedure, Oct 1997 - Dec 2003
25
20
15
10
5
0
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution
Monitor trends and patterns
Monitor/detect changes in health practices
Monitor changes in infectious agents (Outbreak
predicting?)
Evaluate control measures
Portray the natural history of a disease
Generate hypotheses, stimulate research
number of reports
Staphylococcus aureus bacteraemia reports and
methicillin susceptibility, England & Wales
17,500
resistant
15,000
12,500
10,000
7,500
5,000
2,500
0
no information
sensitive
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution
Monitor trends and patterns
Monitor/detect changes in health practices
Monitor changes in infectious agents
Evaluate prevention and control measures
(effectiveness of intervention)
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
Measles/rubella incidence in Macedonia and
immunization schedule changes in the period 1967-1997
600
500
МB/100.000
400
300
200
100
0
1972 M vaccine
(13 months)
Measles
Rubella
1983 МMR vaccine
(13 months)
1987 М revaccine (7 years)
R revaccine (14 years
1997 МMR revaccine
(7 years)
Uses of public health surveillance
•
•
•
•
•
•
•
Detection of sudden changes in disease occurrence
and distribution
Monitoring trends and patterns
Monitoring/detect changes in health practices
Monitoring changes in infectious agents
Evaluation of prevention and control measures
Provide an evidence base for policy and guidance
formulation – future action
Generate hypotheses, stimulate research
MMR vaccination coverage in 1983-2007 and mumps
case distribution in 2007-2009, by year of birth
100
1238
1200
95
1100
90
85
900
Број на заболени
922
814
% Опфат со МР(П) вакцина 75
800
700
600
80
70
697
538
% Опфат со МР(П)
ревакцина
500
65
60
55
400
50
300
45
200
40
100
35
0
30
Year of birth
Institute of Public Health
Vaccination coverage %
1000
19781979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
Number of mumps cases
1300
HIV transmision – corelation between heterosexual
and homosexual (MSM ) 1987 - 2011
18
16
14
heterosexual cases
12
MSM cases
10
8
6
4
2
0
Uses of public health surveillance
•
•
•
•
•
•
•
Detect sudden changes in disease occurrence and
distribution
Monitor trends and patterns
Monitor/detect changes in health practices
Monitor changes in infectious agents
Evaluate prevention and control measures
Provide an evidence base for policy and guidance
formulation
Generate hypotheses, stimulate research
MRSA bacteriemia in children
 proposal to undertake enhanced surveillance of MRSA in
children !!!
Remember….
Surveillance is information
for action!
Types of Surveillance
• Passive surveillance
– Routine reporting through the normal channel
• Stimulated passive surveillance
– Routine reporting through the normal channel
following a special request / stimulus
• Active surveillance
– Public health staff actively seek cases
• Population, specific groups
• Health care facilities
Passive Surveillance
• Health care facilities or providers report cases as they
present to health care facilities
• No specific efforts are made to ensure that all cases
are reported
• Surveillance is integrated into routine health care
delivery system (mandatory reporting)
• Advantages:
The most often in use, routine, long-term trends
• Disadvantages:
• Missing data, lack of motivation, low quality, robust
Stimulated Passive Surveillance
• Health care facilities or providers report cases as
they present to health care facilities
• Surveillance remains integrated into routine
health care delivery (zero reporting)
• Special efforts are made to maximize reporting
– Reminders, visits, guidelines
• Example: Surveillance of AFP
Active Surveillance
• The system does not wait for:
– Patients to come to health care facilities
• Health care workers actively reach out to detect
cases (daily, weekly)
• Surveillance is in addition to the routine health
care delivery
• Early detection, timely prevention ...
• Resource intensive (time consuming, cost)
Sentinel Surveillance
• Reporting of health events by selected health
professionals (GP, hospitals)
• Chosen health care facilities report cases
– Sentinel sites: representing a certain geographic area
(city, region) or a specific reporting group (children...)
• Can be active or passive surveillance
• The surveillance system only captures events in
selected areas.
Sentinel Surveillance
• Advantages
− Rationale – less but better data
− Consistent data – stable sample
− Choice of sentinel sites (motivation, responsibility,
competency, data quality, geographical
distribution, timelines)
• Disadvantages
−
−
−
−
Representativeness? Voluntary principe
Denominator?
Actors rotation
Motivation lost
Syndromic Surveillance
• Syndrome is a complex of symptoms
• Syndromic surveillance focuses on one symptom or
constellation of symptoms (clinical outcomes) rather
than a diagnosed disease
• No need of laboratory confirmation. Hence fast.
• More sensitive, but less specific
• Faster public health interventions
We see only the tip…
"see what we look for!"
Reported
+ specimen
ve
Lab-based
surveillance
Clinical specimen
Seek medical attention
Serological
surveys
Clinical Disease
Infected
Exposed
Syndromic
Surveillance
Key messages
• Remember:
• Surveillance is information for action!
• Good surveillance always influences
decisions in the right direction!!!
Thank you!
Dr Gordana Kuzmanovska
National Public Health Institute,
The former Yugoslav Republic of Macedonia
[email protected]