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Guidelines for the Investigation of Gastrointestinal Illness

Zoonoses (by animals) diseases

Gastroenteritis

Reducing the risk of gastroenteritis at open farms, petting zoos & animal exhibits

Gastroenteritis - viral

Enteric (gastro) diseases

Guidelines for the investigation of gastrointestinal illness
4. Case investigation protocol

Page content: 4.1 Introduction | 4.2 Steps in investigation

4.1 Introduction

Why do we investigate sporadic cases?

Most cases of gastrointestinal illness occur as apparently sporadic cases of illness with no obvious association with each other. It can be very difficult to identify a source of infection from an investigation of a single sporadic case. However, every sporadic case of illness should be seen as having the potential to be part of an unrecognised cluster or outbreak and the investigation should be undertaken with this in mind. Interviewing a number of sporadic cases may be useful in generating hypotheses about a possible source/s of infection amongst previously unassociated cases. This may lead to the identification of clusters or outbreaks of gastrointestinal illness in the community.

The routine follow up of sporadic cases also allows for:

The prevention of further infections from the case
The identification of other cases amongst households and other close contacts of the index case
Identification of disease amongst risk groups (eg food handlers, child care workers
Education and/or feedback to the case, doctor, other contacts and premises
The identification of promotional opportunities to inform and educate the community about preventing the spread of infectious diseases

These key points should be considered when carrying out any gastrointestinal illness investigation:

What is the public health significance of this case?
Does the illness of this case pose a risk to others?
Is this case part of an outbreak?
Are there any other cases, perhaps asymptomatic or undiagnosed?
Is there any evidence for a particular source of this illness?
If so, who else is at risk/what is the susceptible population?
Should this case be further investigated? If so how?

Be wary of accepting the case's supposition that the take-away meal which they consumed some hours before they became ill was the source of their illness. Single and clustered cases of gastroenteritis may sometimes be due to pathogens spread in food and water, but gastrointestinal pathogens (particularly viruses) are often spread from person to person by close contact, environmental sources or contaminated fomites, particularly when hygiene is poor.

Record Keeping

During an investigation of a sporadic case it is critical that clear notes be kept detailing all steps taken during the investigation. These notes should include the completed questionnaire, assessment of all potential risk factors, details of any control measures implemented and any other action taken including a summary of findings. Local government should keep their own records for future reference as the sporadic case may become part of a wider investigation.

Referral to Other Local Government Authority

Cases for follow up will be referred to the local government area in which the case resides. The investigating officer may need to refer investigation of food premises, special care facilities, child care centres etc to other municipalities when a need for follow up is indicated as part of their investigation. In these circumstances, the investigation summary should include the municipality the matter is referred to and if possible the investigating officer.

4.2 Steps in investigation

Gastrointestinal illness investigations must be conducted with care and tact and in a professional manner.

Ensure that confidentiality is maintained throughout the investigation process. Refer to Section 3.4.

4.2.1 Obtain Consent to Contact the Patient

Where notification is from a doctor

Contact the doctor first (so as not to breach patient-doctor confidentiality) and explain that the notification has been referred to you for further investigation. Explain that you seek further information in relation to the case and would like to contact the case to complete your investigation. If, with the doctors consent, you then approach the case, it is important to explain to the case why you are contacting them, and to assure them that the information they provide is kept confidential. In some circumstances, the doctor may wish to contact the patient prior to you contacting them or may prefer to personally obtain the information you require from the patient.

Where notification is from a laboratory or hospital

Contact the laboratory or hospital to find out the name and phone number of the referring doctor/treating doctor, then follow the procedure as per notification from a doctor.

If you have difficulty contacting a doctor, leave a message to advise that you will be contacting the patient the next day unless the doctor informs you otherwise
If the doctor does not give consent, request the doctor to follow up notification and provide the doctor with the appropriate questionnaire
If the doctor does not give consent and is not willing to follow up, report the occurrence to the region who will notify Disease Control Victoria

4.2.2 Interview Case

Clarify the nature and timing of the case's symptoms. Use appropriate questionnaire (see attachments) to determine the following:

Personal details
Clinical symptoms
Occupation/school/child care
Travel
Environmental exposures
Other risk factors
Case finding (see glossary)
Food history - General and 4 day history

4.2.3 Risk factor

There are certain risk factors which indicate that further investigation is required and may present educational opportunities. These risk factors can be broadly categorised as follows:

Occupational
- food handler
- health care worker
- child care worker
Possible source
- environmental
- food
- water
- occupational
- institutional
- contact with other cases
Travel
- overseas
- interstate
- intrastate

4.2.4 Risk Assessment and Risk Management

The following tables indicates the main opportunities to recognise risk factors and then implement procedures to prevent or minimise the risk of further cases.

Risk factor	Risk Assessment	Risk Management
Food handler	assess whether food handler was excluded in accordance with guidelines (see attachment 6) assess whether proprietor has an exclusion policy and it is enforced ascertain whether there are other workplace cases ascertain whether any foods consumed in the workplace are a likely source assess food handling based on HACCP principles/food safety program ascertain any other likely source identify any other risk factor	exclude any food handlers in accordance with guidelines sample any suspected food, water or implicated batches implement clean up and control measures as appropriate review food handling based on HACCP principles/food safety program check for additional cases provide information and educational resources for managers and staff

Risk factor

Risk assessment

Risk management

Health care worker

assess whether health care worker was excluded in accordance with guidelines*
assess whether establishment has an exclusion policy and it is enforced
ascertain whether there are other cases amongst staff or clients
assess any other potential source of infection
assess food handling based on HACCP principles/food safety program
assess infection control policy procedures for effectiveness
identify any other risk factor

exclude any health care worker in accordance with exclusion guidelines*
sample any suspected food, water or implicated batches
implement clean up and control measures where appropriate
review food handling based on HACCP principles/food safety program
review infection control policy and procedures as they relate to the work duties of the case
check for additional cases
provide information and educational resources for managers and staff

* Child care workers and health care workers should be excluded for the same periods as for food handlers (see food handler exclusion guidelines attachment 6) however, hospitals, children's services, nursing homes etc may have their own staff exclusion policies.

Risk factor	Risk assessment	Risk management
Child care worker	assess whether child care worker was excluded in accordance with guidelines* assess whether establishment has an exclusion policy and it is enforced ascertain whether there are other cases amongst staff or clients assess any other potential source of infection assess food handling based on HACCP principles/food safety program assess infection control policy procedures for effectiveness identify any other risk factor	exclude any child care worker or children in accordance with exclusion guidelines* sample any suspected food, water or implicated batches implement clean up and control measures where appropriate review food handling based on HACCP principles/food safety program review infection control policy and procedures as they relate to duties of case check for additional cases provide information and educational resources for managers and staff
* Child care workers and health care workers should be excluded for the same periods as for food handlers (see food handler exclusion guidelines attachment 6) however, hospitals, children's services, nursing homes etc may have their own staff exclusion policies.

Risk factor	Risk assessment	Risk management
Two or more associated cases	assess common link between cases identify any potential source identify other cases identify others at risk identify any other risk factor	sample any suspected food, water or implicated batches implement control measures to prevent ongoing spread from any potential source implement risk management procedures as appropriate where other risk factors are identified check for additional cases provide information and educational resources for cases or families as appropriate

Risk factor	Risk assessment	Risk management
Implicated source	assess whether source implicated by case is likely to be the actual source identify other potential sources identify any other risk factors	sample any suspected food, water or implicated batches implement control measures to prevent ongoing spread from any potential source implement risk management procedures as appropriate where other risk factors are identified check for additional cases provide information and educational resources for case or family as appropriate refer information to another local government where it is suspected that the source may be from that municipality.

Risk factor

Risk assessment

Risk management

Hospital inpatient

identify potential source
identify whether source may have been hospital acquired
identify other risk factors
ascertain whether there are any other cases

sample any suspected food, water or implicated batches
implement control measures to prevent ongoing spread from any potential source
implement risk management procedures as appropriate where other risk factors are identified
check for additional cases provide information and educational resources for case and family where appropriate

Where infection is potentially hospital acquired:

review food handling based on HACCP principles/food safety program
review infection control policy and procedures

Risk factor

Risk assessment

Risk management

Special care facility client

identify potential source
identify whether source may have been special care facility acquired
identify other risk factors
ascertain whether there are any other cases

sample any suspected food, water or implicated batches
implement control measures to prevent ongoing spread from any potential source
implement risk management procedures as appropriate where other risk factors are identified
check for additional cases
provide information and educational resources for case and family where appropriate

Where infection is potentially special care facility acquired:

review food handling based on HACCP principles/food safety program
review infection control policy and procedures

Risk factor	Risk assessment	Risk management
Travel	identify whether onset is consistent with travel/departure timeframe identify other potential source ascertain whether there are any associated cases identify other risk factors	implement control measures if other risk factor determined if source suspected from another jurisdiction, refer information through to other council or state health department provide information and educational resource materials to case and family as required

4.2.5 Health Promotion Opportunities

The investigation of cases of gastrointestinal illness provides important opportunities to inform and educate the case and their families about the spread and prevention of gastrointestinal illness. To support this, Disease Control Victoria has produced a series of pamphlets on gastrointestinal illnesses which are freely available.

Investigations can also provide opportunities to inform and educate the workplace about the spread and prevention of gastrointestinal illness and how this relates to food handling and infection control. The series of pamphlets on gastrointestinal illness, as well as the series on food handling are both freely available to assist in this process.

By following up cases of gastrointestinal illness, areas of specific concern within the municipality can be identified. For example, child care centres, nursing homes, certain types of food premises, may become the target of a specific health promotion intervention initiated by a municipality. This information can also be used to assist in the Municipal Public Health Planning process.

Wider health promotion opportunities are also present, such as working with other local and regional agencies, health care professionals and community groups, to address issues relating to common endemic notifiable gastrointestinal diseases.

An example of a wider health promotion opportunity is developing a series of articles for local papers on safe food handling practices. This information is easily extracted from the food handling pamphlets.

4.2.6 Completion of Investigation

After the investigation has been finalised, return completed questionnaire, completed action section of notification form and provide details of any other action taken or investigations completed (eg inspections of premises, referral of suspect premises to other municipalities) to the Region.

4.2.7 Special Investigations

These investigations will be initiated and coordinated by Disease Control Victoria with assistance provided by the relevant region and local government. The type of gastrointestinal illnesses being investigated often require specialist public health interventions. eg Hepatitis A, typhoid, paratyphoid, listeriosis, HUS/VTEC.

Guidelines for the investigation of gastrointestinal illness index

Related information

From Diseases:

Enteric (gastro)

Gastroenteritis

Gastroenteritis - viral

Guidelines for the Investigation of Gastrointestinal Illness - Introduction

Zoonoses (by animals)

From Guidelines:

Reducing the risk of gastroenteritis at open farms, petting zoos & animal exhibits

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Guidelines for the investigation of gastrointestinal illness4. Case investigation protocol

4.1 Introduction

4.2 Steps in investigation

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Guidelines for the investigation of gastrointestinal illness
4. Case investigation protocol