Infectious Disease Epidemiology

Surveillance

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Definition “Ongoing systematic collection, analysis,

and interpretation of health data essential to the planning, implementation, and evaluation of public health practice, as well as the timely dissemination to those who need to know”

• Centers for Disease Control. Comprehensive plan for epidemiologic surveillance. 1986

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Public Health Law - Communicable Disease Control

Reporting and surveillance Investigation as to source Examination Treatment Isolation/quarantine

with or without judge’s permission order with or without a warning of an order

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Reporting Legislation requires the report

name, address, locating and demographics laboratory data clinical treatment source, contact data

Reportable by; Laboratory Health professionals

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Case definition Defined by government

As part of regulations or Act includes disease of unusually high numbers Or disease with unusual manifestations ( high

fatality) Laboratory test component Clinical Or both Ad hoc

Take an inclusive list of 80-90% of first 3-5 presenting cases at least

Be aware that agent may change, and hosts may become immune.

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Emerging and re-emerginginfections

From MMWR 2003;52:241-8

Network of Singapore cases of SARS as of April 2,2003.

ANN JOLLY, 2 APRIL 2003

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Surveillance & Management Ensure the case, and contacts are properly

managed Monitor the number of cases for unusual changes

risk, manifestation, affected population, geographic area

Consists of : collection compilation analysis dissemination

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Investigation/contact tracing Case is treated, educated and questioned

about possible exposures The names of the contacts or sources are

reported to public health officials Then the contacts/sources are located,

examined, treated and educated

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Public health data

Laboratory test

Physician report

Laboratory test

Physician report

Public Heath

DepartmentComputer or

card file

Public health nurse

Contact of case

Public Health

Department

Case

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Confidentiality

Disease reporting individual’s right to privacy is being

violated justification is that it benefits that person or protects the public health

Contact tracing/ partner notification Duty to warn

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Tasks1. Set objectives

Monitor geographic and temporal trends Investigate Prevent Monitor occurrence, without intervention

for health system planning Monitor for further study

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Tasks 2. Collect data

Disease case reports (notifications) Laboratory reports Death certificates Schools Sentinel surveillance sites Animal reports

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Tasks3. Perform investigations

Source Route

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Tasks4. Organise data

Output aggregate data from reports by time place person

Calculate rates, confidence limits Tabulate, graph

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Tasks5. Analyse and interpret

Compare current data with past experience, in terms of;

Seasonality Space Error,

alpha or beta (statistical) lab error calculation data entry

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Tasks6. Disseminate

Regional Medical Officer of Health Provincial Epidemiologist Chief Medical Health Officer Infectious disease specialists Public health units Public health inspectors

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Tasks7. Hypothesis formation

Formulate i.e. waterborne in one municipality

Identify further data to substantiate Obtain data Organise Analyse and interpret Refute or prove hypothesis

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Tasks8. Recommend/implement control measures

Establish objectives for control barriers to infection at any point(s) in

host/agent/environment cycle Recommend control measures Implement control measures Evaluate and monitor control measures

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Tasks9. Distribute findings

Locally Provincially Nationally Internationally

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Tasks10. Evaluate surveillance system

Data sources timeliness accuracy completeness

Use and relevance of data Are surveillance objectives being met? Recommend and implement changes

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References

Teutsch, SM and Churchill, RE, eds. Principles and practice of public health surveillance. Oxford University Press, 1994

Morbidity and Mortality Weekly Report. Supplement, December 1992. Proceedings of the 1992 International Symposium on Public health surveillance. Vol 41.

Thacker SB, Berkelman RL. Public health surveillance in the United States. Epidemiologic Reviews 1988;120:164-188