Introduction to Public Health Surveillance Dr Giri Shankar Lazareto de Mahon, Menorca, Spain 24 September –12 October 2012 &

Introduction to Public Health Surveillance

Dr Giri Shankar

Lazareto de Mahon, Menorca, Spain24 September –12 October 2012

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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

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Outline of Lecture

Definition of Surveillance

Surveillance Loop

Uses of Surveillance with examples

Summary

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What is Surveillance?

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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?

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“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

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Surveillance is

Information for action

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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

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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

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Health care system

Surveillance centre

Reporting


An

alysis, in

terpretation

Event

Action

Data

Information



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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

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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

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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

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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

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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

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Health care system

Surveillance centre

Reporting


An

alysis, in

terpretation

Event

Action

Data

Information



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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

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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

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Health care system

Surveillance centre

Reporting


An

alysis, in

terpretation

Event

Action

Data

Information



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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

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Surveillance is


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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?

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• 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

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Notifications of Meningococcal Infections

Cases of group B and C meningococcal disease in England and Wales, by age group -1998-2004

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• 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

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TB notification and death rate England and Wales, 1913 - 2000 &

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• 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

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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

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Age and sex distribution of confirmed H1N1v cases in the UK, 30 June 2009

(n= 6766)(FluZone) &

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Regional Spread of cases - May

10 May 31 May

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Regional spread of cases - June

05 June12 June

19 June26 June

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UK epidemiology: treatment phase

RCGP weekly ILI rate 2009/10 and recent years, England

0

50

100

150

200

250


ILI r

ate

per 1

00 0

00

Week-ending date



Switch to 'treatmentonly' phase


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UK epidemiology: launch of National Pandemic Flu Service

RCGP weekly ILI rate 2008/09 and recent years, England

0

50

100

150

200

250


ILI r

ate

per 1

00 0

00

Week-ending date




NPFS Launched and Schools close for summer


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UK epidemiology: end of first wave

RCGP weekly ILI rate 2009/10 and recent years.

0

50

100

150

200

250


ILI r

ate

per 1

00 0

00

Week-ending date





schools re-open


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UK epidemiology: end of first wave

RCGP weekly ILI rate 2009/10 and recent years.


0

50

100

150

200

250


ILI r

ate

per 1

00 0

00

Week-ending date





schools re-open

Schoolhalf-term break

&&

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• 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

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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

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• 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

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Staphylococcus aureus bacteraemia reports and methicillin susceptibility England & Wales

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• 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

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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

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• 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

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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

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Cumulative reports of Pneumococcal Disease due to the seven serotypes IN Prevenar™ : Children < 2 Years in E&W by Epidemiological Year

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Cumulative reports of Pneumococcal Disease due to the seven serotypes NOT in Prevenar™ : Children < 2 Years in E&W by Epidemiological Year

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• 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

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MRSA bacteraemia in children

proposal to undertake enhanced surveillance of MRSA in children

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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

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Surveillance is


Remember

Documents

Introduction to Public Health Surveillance Dr Giri Shankar Lazareto de Mahon, Menorca, Spain 24 September –12 October 2012 &