Outbreak Management: The SARS Outbreak in Epiville
D. Background of the Epiville SARS Simulation outbreak

The case definition is a list of specific criteria used to decide whether or not one has the disease under investigation. The case definition of the Epiville SARS outbreak is a visitor to, or resident of the Amoy Apartment Complex or a worker at Star Hospital, who has onset of respiratory flu-like symptoms (high fever, cough, difficulty in breathing) from 10th August 2003 to 23rd August, 2003, without other apparent cause. The Epiville General Hospital suspects that the strange disease is the severe acute respiratory syndrome (SARS) although they are yet to conduct diagnostic tests to confirm the same. A clinical case is defined as an acute respiratory illness lasting ? 2 weeks and with onset from 10th August 2003 without other apparent cause for a person living in the Amoy Apartment Complex. A suspected case is a clinical case epidemiologically linked to a clinical case through a common household residency. All other clinical cases are considered probable.

The choice of case definition influences the scope of an outbreak investigation. For instance, if the case definition is too broad, the epidemiologist will include in their investigation all other illnesses that meet the stated clinical criteria (CDC, 2012). On the other hand, if the case definition is too strict, the investigation will only include people confirmed to have the disease (CDC, 2012). In the Epiville outbreak, for instance, the case definition includes both residents of, and visitors to the Amoy Apartments complex - implying that the epidemiologist will have to focus their outbreak investigation on both residents and visitors. On the other hand, if the case definition only considered residents, the investigation would not bother with non-residents and would only focus on the population living within the Complex.

Factors to Consider when Developing a Case Definition

The epidemiologist considers several factors when formulating a case definition. These are:

i) Person – demographic characteristics of the affected population including their age, sex, occupation, and race

ii) The geographical coverage of the suspected outbreak (place) such as the healthcare facility, street, town, or apartment complex

iii) The time representing the onset of illness in days, weeks, months, or years. Delineating the time period helps to exclude similar illnesses that are not related to the outbreak under investigation

iv) The clinical features associated with the illness under investigation, such as symptoms

v) Whether or not confirmatory laboratory tests have been carried out – this helps in grouping cases as either confirmed, probable, or suspected

vi) The aim of the outbreak investigation for which the case definition is developed – for instance, if the aim of the investigation is to know if anyone in a particular area has symptoms of a communicable disease so that they can begin planning on what actions to take, the case definition may be broad to identify all possible cases (CDC, 2012). However, if the aim of the investigation is to determine the causes of an outbreak, a strict case definition may be adopted to ensure that only people confirmed to have the disease are included (CDC, 2012).

Epiville SARS Simulation Outbreak in terms of PPT

Elements

Descriptive Variables

The Epiville Outbreak

Person

Age group, sex, occupation, race, and exclusion criteria of the affected population

The outbreak disproportionately affects older individuals aged over 50

Place

Geographical location

Facility

The outbreak is localized within Amoy Apartment Complex and Star Hospital

Time

Onset of illness

between 10th August 2003 and 23rd August 2003

The Epiville SARS outbreak is localized within the Amoy Apartments complex and Star Hospital, with an onset from 10th August to 23rd August 2003, and disproportionately affects older individuals above the age of 50

Steps in the Epiville SARS Outbreak Investigation

i) Define the epidemic by defining the clinical cases, the population at-risk of illness, and calculating attack rates

ii) Examining the distribution of cases by person, place, and time – the epidemiologist does this by reviewing charts of patients, creating lists of names of patients who have died from the disease to identify the patients’ profile, including their residence and age group.

iii) Look for combinations/interactions of relevant variables

iv) Developing hypotheses about the cause of the illness based on existing knowledge of the disease and relationships to diseases whose etiology is known

v) Testing the hypotheses through conduction of an appropriately-designed study and collection of additional data if necessary

vi) Recommend control and management measures such as quarantine, isolation, and public sensitization on prevention and control

E. Summarize the techniques used in the Epiville SARS Simulation outbreak investigation

Surveillance Methods used to Ascertain Cases

Surveillance is the continuous collection and analysis of data on cases that is not necessarily followed by subsequent action. Surveillance methods used to ascertain cases include:

i) Review of case records including centralized disease registries and hospital discharge notes

ii) Microbial laboratory monitoring

iii) Hospital reporting of confirmed cases to the Department of Health

iv) Physical counts and visits to the Amoy Apartment Complex

v) Periodic telephone calls to healthcare facilities/individuals/laboratories

Number of Suspect and Probable Cases