Outbreak investigation will confirm that there is an outbreak, ensure the infecting organism is correctly diagnosed, and a case definition is established and tracked to who is infected and who is at risk. Outbreak management from the investigation will ensure correct infection control practices are in place, help with communicating the findings and assist in presenting a hypothesis of the outbreak.  The investigation process involves a number of steps.

Step 1: Recognise the outbreak and prepare to investigate

Determine that an outbreak exists

The background occurrence of the infection rate for the infectious disease needs to be determined for comparison with current infection rates to determine the presence of an outbreak

Implement immediate outbreak management control measures

Notify all employees and management

Nominated person (IPC lead/manager) to notify the local public health notification authority

Outbreak coordinator/management team to be involved

 

Step 2: Verify the diagnosis and confirm the outbreak exists

Review each case to ensure that there are no discrepancies between diagnosis and laboratory findings

Confirm cases and identify infecting agents if possible

 

Step 3: Establish case definition and identify the case

Establish standard criteria to decide whether a person has the disease of concern e.g.,

Influenza case definition 

Gastroenteritis case definition

Norovirus case definition

C. Difficile case definition

RSV case definition

Scabies case definition 

COVID-19 case definition 

 

Step 4: Characterise the outbreak by person, place, and time

Compile documentation by a designated employee (IPC lead) regarding all affected residents, employees, and visitors. The local public health notification authority may provide a tracking form for this information.

The following information is required

1) Person's name

2) Date of birth/age

3) Date of admission

4) Location of resident in the facility, section, room number, and or bed

5) Date and time of symptom onset

6) Presenting symptoms

7) Date symptoms resolved or date of last symptoms

8) Specimens collected, when collected, and results

 

Step 5: Determine who is at risk

Identify the risk groups and the number of affected or at-risk residents and initiate the outbreak management control measures required for the identified infectious disease, which may include

1) Isolating and or cohorting residents

2) Standard and transmission-based precautions appropriate for infectious disease

3) Restricting the movement of residents, employees, and visitors.  This may include lockdown of an area or the facility

4) The exclusion of high-risk activities, such as the closing of dining rooms and therapy areas

5) Screening of residents while in isolation and cohorting contacts may involve employee screening

6) Increase frequency and efficiency of cleaning using recommended cleaning agents

7) Prophylactic treatment/immunisation

8) Antibiotic restrictions

9) Health information and advice to be given, to all residents, employees, and visitors

 

Step 6: Implement ongoing control/prevention measures

Outbreak management control measures will need to be regularly reviewed and adjusted to contain and manage the outbreak.

Standard and transmission-based precautions will need continual implementation during the outbreak to

1) Restrict the spread from the affected case(s)

2) Interrupt the chain of infection

3) Interrupt transmission or reduce exposure

4) Reduce susceptibility to infection

 

Step 7: Communicate findings

Document the type and time of implementation of infection control measures. Monitor factors contributing to or affected by the outbreak and note any changes.

 

Step 8: Develop a hypothesis (how, why, and when?)

Develop hypotheses from the information gathered on the potential source of infection 

When did the infection occur?

How did the infection occur?

Why did the infection occur? 

 

Step 9: Test the hypothesis with facts

Analyse the data, compare risk factors among affected cases, and identify the rate of cases. Determine if the theory explains the situation for most cases.