What You Will Learn
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It is the continuous scrutiny and watchfulness of disease and factors that determine the occurrence and distribution of the disease and other conditions of ill-health with sufficient accuracy and completeness to provide basis for effective control.
Disease surveillance involves
- Collection
- Collation
- Evaluation, and
- Dissemination of information to those in position of taking action
- To define the demographic, temporal and geographic distribution of disease
- To test hypotheses regarding causation or transmission
- To detect outbreaks or new strains,
- To guide or evaluate disease control strategies
- To assess cost of a condition
- To detect changes in public health practice
- To facilitate planning and identify research needs, and/or
- To define the natural history of disease
- Prepare and distribute surveillance reports to health care professionals participating in disease prevention and control activities.
- Active surveillance
- Passive surveillance
- Epidemiological surveillance
- Nutritional surveillance
- Demographic surveillance
- Sentinel surveillance
Epidemiologic surveillance
- It is the ongoing systematic collection, recording, analysis, interpretation, and dissemination of data reflecting the current health status of a community or population.
- Surveillance is based on both passive and active data collection processes.
Active surveillance
- Refers to daily, weekly or monthly contacting of physicians, hospitals, laboratories, schools or others to “actively” search for cases.
- It is more time- and resource- intensive, relative to passive surveillance, and therefore less commonly used in emergencies, but it is more complete than passive surveillance.
- It is used during high disease frequencies and also during outbreaks
- E.g.
- Health surveys
- Census
Passive surveillance
- Done on a routine/regular basis i.e. data taken by institution that see patients are being routinely or regularly submitted for analysis. There is no active search for cases
- Relies on cooperation or compliance of health-care provider (laboratories, hospitals, private practitioners) to report the occurrence of diseases to a higher administrative level, where the data is compiled and analyzed to monitor disease patterns and identify possible outbreaks
- It is the most common type of surveillance for
- Humanitarian emergencies
- Communicable disease
- The detection of vaccine-preventable disease
- It is often incomplete; because there are few incentives for health workers to report.
- E.g.
- Hospital and billing data
- Vital statistics: births and deaths
Nutritional surveillance
- It is a systematic approach used to detect malnutrition and identify populations at risk of suffering from it.
- Usually done for population of <5yrs of age
- Then, Classify population into:
- Stunted;
- Having kwashiorkor;
- Marasmic;
- Underweight;
- Obese;
- Well nourished
Demographic surveillance
- Relating obtained data to demographic data (age, sex, marital status ...)
- Demographic surveillance systems (DSS) work by monitoring individuals, households and residential units in a well-defined geographic area, known as a demographic surveillance area (DSA).
- They begin with an Initial Census, which defines and registers each individual in the target population, as well as age, sex and marital status. Data are collected, at this stage, on household composition, religion, ethnicity, education levels, occupation, household wealth and access to facilities such as water and sanitation.
- Subsequently, regular data collection monitor changes to this population by gathering information on births, deaths and migrations. These update rounds also record other key events such as marriage, divorce, pregnancy and changes in employment status.
Sentinel surveillance
- You carry out a study on a specific condition, its rate of occurrence and its stability within a particular subgroup of a population. The data obtained are generalized for the whole population.
- To assess burden of a disease on a population
- Sentinel surveillance system is used when high-quality data are needed about a particular disease that cannot be obtained thru a passive system.
- Inadequate supervision
- Lack of logistic support
- Frequent turn-over of staff
- Inadequate training
- Deficient or unharmonized data
- Lack of political will, and therefore depending on donor
- Data falsification
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Definition: Epidemics is the increase in the number of cases of a disease in a population, in excess of the usual number for that place and that particular time.
Other terms- PANDEMIC – increase in the number of cases of a disease in a particular place, over a period of time, in excess of the usual, that has spread beyond a country
- ENDEMIC – habitual presence of a disease in a place throughout the year
- To help define magnitude of outbreak in terms of time, place and person
- To identify factors responsible
- To identify cause, source and route of transmission or mode of transmission
- To prevent future occurrence
- Verify diagnosis
- Confirmation of existence of epidemics
- Defining the population at risk
- Rapid search for all cases and their characteristics through medical survey, etc.
- Data analysis in terms of time, place and person, for the disease.
- Formulation of hypothesis
- Testing of hypothesis
- Evaluation of ecological factors
- Further investigation to determine population at risk
- Report writing
- Disseminate the findings
- It is a team approach
- Get the history of disease from patients while treating them
- Point-source epidemics – because of a single exposure
- Propagated epidemics – because of multiple exposures
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ISOLATION – You isolate people with the disease
QUARANTINE – you quarantine those with suspected cases of the disease
PRIMORDIAL PREVENTION – government policies/legislations that are in place to prevent the disease e.g.
- Adequate town planning in a population that has never been exposed
- In Onchocerciasis, people should not build houses around riverine areas
Practice Questions
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