- Reason for surveillance
- Definitions
- Notification criteria and procedure
- The disease
- Case investigation
- Contact management
- Epidemiological investigation
- Additional resources
1. Reason for surveillance
- To identify the source and so prevent further cases.
- To monitor the epidemiology and so inform the development of better prevention strategies.
2. Definitions
Clusters of two (or
more) confirmed cases or probable cases should
be notified.
Probable case
A person
within an institution who develops vomiting or diarrhoea within an incubation
period of when at least one other person at the institution was infectious with
vomiting or diarrhoea (i.e. overlapping infectious and incubation periods).
Confirmed case
Isolation of a pathogen consistent with the aetiology of illness from a vomitus or stool specimen in a probable case.
Cluster
Any two (or more) confirmed cases or probable cases in
the same institution where one case develops vomiting or diarrhoea within
an incubation period* following when at least one other person at the
institution was infectious* with vomiting or diarrhoea.
*Infectious
and incubation periods are given in ‘Section 4. The disease’ (table page 4).
PHU investigation and assessment should be based on the appropriate timeframes
for the suspected pathogen, given the clinical presentation of cases. However,
to help facility staff understand when an outbreak may be occurring, the
following time frames are given in the respective Gastro Packs:
- Gastro
Pack for Childcare Centres: when two or more children or staff have
sudden onset of vomiting or diarrhoea in a 2 day period.
- Gastro
Pack for Hospitals and Aged Care Facilities: when two or more people
have sudden onset of vomiting or diarrhoea at the one time in any institution.
“At one time” means that at least one person with vomiting or diarrhoea is
thought to have been infectious when at least one other person at the
institution has vomiting or diarrhoea. This includes situations where patients
are received from another facility/agent.
Institution
Any residential environment or organisation with
a responsibility to care for a defined group of individuals, such as:
- Aged care facilities, disability and dementia care facilities
- Early education and child care centres
- Healthcare settings such as hospitals and rehabilitation services
- Schools (particularly boarding schools)
- Camps and excursions
- Military and other Defence Force facilities
- Correctional facilities
- Other residential environments such hostels and university/college residences.
3. Notification criteria and procedure
Gastroenteritis among two or more people of any age in an institution is to be notified by:
- CEOs of hospitals, ACFs and other institutions
(as defined above) or their delegates
- Medical practitioners.
All
notifications should be made by phoning the local PHU on 1300 066 055.
4. The disease
Infectious agents
Numerous
enteric pathogens, including viruses, bacteria and parasites, as well as toxins
produced by bacteria, can produce gastroenteritis outbreaks. Noroviruses are
the most common cause of large outbreaks in institutions.
Mode of transmission
Gastroenteritis is transmitted in different modes, including:
- Person to person spread
- Ingestion of contaminated food or drink
- Contact with contaminated surfaces
- Ingestion of airborne droplets has been suggested for norovirus.
Timeline
Incubation periods and clinical features of selected agents of gastroenteritis are presented in the table1 below.
| Bacillus cereus (toxin) |
1-6 hours (vomiting)
6-24 hours (diarrhoea) |
Malaise, vomiting and/or diarrhoea |
24-48 hours |
Foodborne |
- Food source has been identified and/or eliminated, or
- No new cases for 48 hours after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Campylobacter spp. (bacteria) |
1-10 days |
Fever, nausea, abdominal cramps and/or diarrhoea (sometimes bloody) |
2-5 days |
Food or water borne; person to person (rarely) |
- Food or water source has been identified and/or eliminated, or
- No new cases for 3 weeks after the last episode of
vomiting or diarrhoea in last case
|
|---|
Clostridium
difficile
(toxin) |
Unknown |
Ranges from mild, self-limiting diarrhoea to a
serious form of the disease, known as pseudomembranous colitis. Vomiting not
common. |
Days to weeks |
Person to person |
On advice from CDB |
|---|
| Clostridium perfringens (toxin) |
6-24 hours |
Abdominal cramps, diarrhoea and/or nausea |
24-28 hours |
Foodborne |
- Food source has been identified and/or eliminated, or
- No new cases for 48 hours after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Giardia spp. (parasite) |
3-25 days |
Abdominal cramps, diarrhoea, excessive gas,
fatigue, floating greasy stools |
May last for long periods of time if not treated |
Person to person; water borne; foodborne
(rarely) |
- Water (or food) source has been identified and/or eliminated, or
- No new cases for 2 weeks after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Norovirus (virus) |
24-48 hours
(range 10-50 hours) |
Vomiting, fever, nausea, abdominal cramps,
diarrhoea and/or headache
|
24-60 hours |
Person to person; food or water borne |
No new cases for 3 days (72 hours) after the
last episode of vomiting or diarrhoea in last case |
|---|
| Rotavirus (virus) |
1-3 days |
Vomiting, watery diarrhoea and/or fever –
infants, younger children, elderly and immunocompromised are vulnerable to
severe disease |
4-6 days |
Person to person |
No new cases for 7 days after the last episode
of vomiting or diarrhoea in last case |
|---|
| Salmonella spp.(bacteria) |
6-72 hours |
Headache, fever, abdominal cramps, diarrhoea and/or nausea |
4-7 days |
Foodborne; person to person |
- Food source has been identified and/or eliminated, or
- No new cases for 2 weeks after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Shigella spp. (bacteria) |
24-72 hours (occasionally up
to 7 days) |
Abdominal cramps, fever and/or diarrhoea
(sometimes mucoid or bloody) |
4-7 days |
Person to person; foodborne |
- Food source has been identified and/or eliminated, or
- No new cases for 2 weeks after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Shiga toxin producing E. coli, STEC (bacteria) |
2-8 days |
Diarrhoea (sometimes bloody), abdominal cramps,
vomiting and/or fever – children and elderly are vulnerable to complications e.g.
HUS |
2-7 days |
Foodborne; person to person |
- Food source has been identified and/or eliminated, or
- No new cases for 2 weeks after the last episode of
vomiting or diarrhoea in last case
|
|---|
| Staphylococus aureus (toxin) |
0.5-8 hours |
Abdominal cramps, vomiting and/or diarrhoea |
24-48 hours |
Foodborne |
- Food source has been identified and/or eliminated, or
- No new cases for 12 hours after the last episode of
vomiting or diarrhoea in last case
|
|---|
- Adapted from: SA
Health. Guidelines
for the Management of Gastroenteritis Outbreaks in Residential Environments in
South Australia. March 2016. Government of South Australia. List of
causative pathogens is not intended to be complete.
- Symptoms may not be present in all cases
Symptoms of viral gastroenteritis usually last between 24 and 48 hours but can sometimes be longer. Cases are usually infectious for at least 48 hours after symptoms cease. Outbreaks where diarrhoea was the
only/predominant symptom are unlikely to be caused by norovirus or rotavirus,
and consideration of a food or other sources is important.
Clinical presentation
Clinical symptoms vary depending on the causal agent and may include nausea, vomiting, diarrhoea, abdominal pain, myalgia, headache, malaise and low-grade fever.
5. Case investigation
Response times
Investigation
On same working day of notification of two or more probable or confirmed cases in an institution, begin follow-up investigation.
Notify the Communicable Diseases Branch (email NSWH-Enteric@health.nsw.gov.au)
within one working day of notification. If within a licensed aged care
facility, include the Aged Care Quality and Safety Commission (ACQSC, nsw_office@agedcarequality.gov.au)
in the email notification.
Data entry
On the same working day of notification ensure that the initial
information is entered into NCIMS and notified to CDB.
Notify CDB (and ACQSC if a licensed ACF) by using the “institutional
outbreak summary” template from NCIMS. Although the template will mostly
auto-populate, the PHU should check that the following fields have been
completed:
- Owning jurisdiction (PHU)
- Name of the facility
- Type of facility
- Date notified
- Onset date of first case
- Whether first case was staff, resident/child
(“non-staff”) or other
- Number of cases – non-staff, staff
- Number at risk – non-staff, staff
- Symptoms of cases
- Number of cases recovered so far
- Samples collected
- Infection control measures implemented
- Suspected cause of outbreak e.g. viral person to
person, foodborne
- Deaths during the course of the outbreak should
be reported to CDB using the template.
To close an outbreak,
complete the “Date outbreak / exposure closed” field in NCIMS (General
question package) and change the event/cluster status to “closed”. This should
be completed within one month of notification if cases are no longer occurring,
or within one month of the last case in outbreaks which last longer.
Note: An institutional
outbreak summary form from NCIMS does not need to be re-submitted to CDB at the
closure of an outbreak of gastroenteritis.
Response procedure
The response to a notification will be carried out in collaboration with the cases' health carers and the institution that has been affected. But regardless of who does the follow up, PHU staff should ensure that action has been taken to:
- confirm the onset dates and symptoms of the illness with cases
- confirm results of relevant pathology tests, or recommend that tests be done
- review control measures put in place by the institution
- identify the cases that are in a high risk occupation (such as a food handler, child care attendant, carer)
- ensure the facility has access to the appropriate Gastro Pack.
Where food is suspected as the cause of the outbreak, request the NSW Food Authority to conduct an environmental investigation. A joint inspection of the facility is recommended. Refer to Foodborne Illness Outbreak protocol and seek advice from Communicable Diseases Branch.
Case management
Treatment
Treatment of cases is the responsibility of the health care provider.
Investigation
The response
to a notification should be carried out in collaboration with the cases' health
carers and the institution that has been affected. The following steps are a
guide to the investigation of gastroenteritis outbreaks in institutions. The
response to the outbreak will depend on the suspected mode of transmission,
cause of illness and whether there is ongoing risk of transmission. Steps marked with an asterisk (*) should
have priority:
- If
notified by someone other than the person in charge of the institution, contact the person in charge of the institution and
advise them you are investigating a suspected outbreak*
- Confirm
the existence of the outbreak by determining:
- the
number of staff and non-staff ill*
- the
number of staff and non-staff at risk*
- onset
dates and symptoms of those ill*
- whether
any staff, carers or food handlers were ill before the outbreak and worked
while symptomatic*
- severity
of illness, including any hospitalisations or deaths, and duration of symptoms
- name
and phone numbers of contact persons and if needed, exposed persons
- menus
for at least 3 days before the first case's onset of symptoms, if food is
suspected as the source of illness.
- Ensure
the facility has access to the appropriate Gastro Pack and other guidelines
(see Section 8. Additional Resources).
- Encourage
the collection of stool specimens from symptomatic cases wherever possible –
ideally at least one specimen for every six cases as soon as practical after
symptom onset, and tested for standard bacterial (MC&S) and viral
pathogens*.
- Liaise
with the receiving laboratory about testing requirements and obtaining results.
- Develop
an epidemic curve to assist in establishing the mode of spread.
- Generate
hypotheses on the source of the agent, the mode of transmission and the
exposures that caused the disease*.
- Advise
on immediate control measures to prevent further cases*.
- Identify
the cases that are in a high risk occupation (such as a food handler, child
care attendant, carers), exclude from work where appropriate – see Isolation
and Restriction below*.
- Monitor
the situation to determine the effectiveness of control measures and the need
for further intervention*
Where food
is suspected as the cause of the outbreak, request the NSW Food Authority to
conduct an environmental investigation by sending a completed Environmental
Investigation Request Form to investigation.support@foodauthority.nsw.gov.au.
A joint inspection of the facility is recommended. Refer to the Foodborne
Illness Outbreak Protocol and seek advice from CDB.
If a notifiable
medical condition is detected in a case, create separate event(s) for each case
and for each confirmed result in NCIMS and link it to the NCIMS record for the
outbreak. If applicable, complete the standard public health response for the
condition.
Education
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission. Emphasise the importance of hand washing, particularly after going to the toilet, changing nappies, before eating and preparing food.
Letters and resources
for facilities are available in the Gastro
Pack for Hospitals and Aged Care Facilities, and Gastro
Pack for Child Care Centres, as well as in the ID
Complementary Operating Procedures on PopNet (see 8. Additional
resources).
Provide a verbal or written report for the manager of the institution or facility which details control and prevention measures.
Isolation and restriction
- Cases who are healthcare workers, food handlers,
carers for children or carers for the elderly should not attend work until at
least 48 hours after symptoms cease.
- Cases who reside in the institution should be
cohorted (separated from non-infected residents) if possible – this must
include separate hand washing, toilet and bathroom facilities. Where this is
not possible, consider cohorting staff.
- Cases who do not reside in the institution
should be strongly encouraged to not attend the facility for at least 48 hours
after their last episode of vomiting and/or diarrhoea.
- Consider recommending closure of the facility to
new admissions if the outbreak continues and new admissions are considered to
be at risk. This decision to close the facility to new admissions should be
made by the facility in conjunction with advice from the PHU.
Environmental evaluation
A basic
environmental evaluation is recommended for all outbreaks. Most evaluations may
be completed over the phone. Occasionally, a site visit by PHU staff may be
warranted to aid investigations into the source of infection and review control
measures. An investigation tool (template) has been developed to assist this
process and is available in the ID
Complementary Operating Procedures on PopNet (see 8. Additional
resources).
- Review hand washing facilities and adequacy of
hand washing practices
- Review environmental clean-up procedures – surfaces
exposed to infectious faecal matter or vomitus should be cleaned (refer to the
Department of Health Fact Sheet); bleach 0.1% is required to inactivate
norovirus
- Where a food is suspected, request the NSW Food
Authority to conduct an environmental investigation by sending a completed Environmental
Investigation Request Form to investigation.support@foodauthority.nsw.gov.au
and follow the Foodborne
Illness Outbreak protocol
- Where water is suspected as a source,
environmental evaluations should involve local environmental health officers,
Environmental Health Branch and Local Council, where appropriate.
Declaring an outbreak over
The end of
an outbreak should be determined on a case-by-case basis, and will be decided
by the PHU leading the investigation by considering all available evidence. Considerations
should include:
- the aetiology of the outbreak:
- if confirmed or strongly suspected – it is
recommended to wait at least two average
incubation periods for that organism after the last episode of vomiting or
diarrhoea in last case (see Table 1)
- if unknown or viral gastroenteritis is suspected
– it is recommended to wait at least 72
hours after the last episode of vomiting or diarrhoea in last case
- if multiple pathogens are suspected, it is recommended to wait for
whichever period is longer
- if case monitoring has been adequately completed
- if appropriate control measures and precautions
have been taken – if a source of infection was implicated if that source
between removed/restricted/decontaminated
- the type of institution affected and if
residents are especially vulnerable to severe disease
- if cases have been isolated with strict
infection prevention and control measures, or excluded from attending the
institution – in such situations, it may be possible to declare the outbreak
over after one incubation period, and/or reduce some control measures (e.g.
temporary closures of affected facilities/wards)
- if additional information or evidence needs to
be collected prior to declaring the outbreak over.
If the
decision to close an outbreak deviates from 72 hours after the last episode of
vomiting or diarrhoea in the last case, the PHU should communicate the
rationale to the institution (i.e. specific pathogen, vulnerability of
residents, good control, etc.) to avoid any confusion about how this decision
may differ from previous advice.
After an
outbreak is declared over, provide advice to the manager of the institution to:
- continue to monitor residents and staff for illness
for at least another week as infection may recur despite the time elapsed
between cases
- note a potential for sporadic gastroenteritis to
occur in non-outbreak situations, and that PHU staff can assist in
differentiate between these events and outbreak cases where required
- note and report any deaths that occurred after
the outbreak, including whether the deceased was part of the outbreak
- gradually resume some activities and discontinue
some highlighted control measures (where appropriate)
- maintain standard precautions for all residents
at all times.
6. Contact management
Secondary cases should be anticipated in persons exposed to the faeces or vomitus of cases. Staff and residents should be given information about the outbreak and how to prevent infection and placed under surveillance.
No specific treatment is recommended for asymptomatic contacts.
7. Epidemiological investigation
Where available data indicates that an unidentified source remains an ongoing risk, then a cohort or case-control study may be required to identify the source.
Refer to Foodborne Illness Outbreak protocol and seek advice from Communicable Diseases Branch.
8. Additional resources
The
following fact sheets and guidelines are available to assist in managing
gastroenteritis in various institutional settings:
Guidelines
Fact sheets
Templates and PHU resources