 
|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Journal of the New Zealand Medical Association,
20-February-2004, Vol 117 No 1189
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Norovirus outbreaks in a hospital setting: the role of
infection control
Sarah Lynn, Julianne Toop, Carl Hanger and Nigel
Millar
Noroviruses (Norwalk-like viruses), previously known as
small round structured viruses, are a common cause of outbreaks of viral
gastroenteritis. The illness is characterised by rapid onset of nausea and
vomiting, often projectile, along with diarrhoea. The symptoms are usually mild
and self-limiting, with a mean duration of illness of 12–60 hours. Relapse
is uncommon but recognised and mortality rates are low, even in hospital
outbreaks. The attack rate is around 50% and the infective dose is as small as
1–10 virus particles. The incubation period is 24–48 hours and
excretion of the virus in faeces can continue for up to 7–10 days.
Transmission is by person-to-person contact through aerosol or direct contact,
or through consumption of food handled by an infected food worker.
Outbreaks have been described in a number of settings with
most exposures in New Zealand occurring in restaurants through contaminated
food.1 Hospitals and rest homes are also
affected, resulting in morbidity for patients and staff, staffing shortages,
hospital disruption and ward closure. Prompt recognition and infection control
measures can minimise the consequences. We report our experience of two NV
gastroenteritis outbreaks that occurred in separate geriatric rehabilitation
wards within an 18-month period, and the role of infection control in limiting
their spread.
MethodsSetting
The two outbreaks occurred in separate rehabilitation wards for older people.
The hospital described has five wards (131 beds) for geriatric rehabilitation
and two wards (44 beds) for psychogeriatric patients. The first outbreak
occurred during winter in a 25-bed ward occupied by 28 patients at the time of
the outbreak. This ward provides rehabilitation for mainly post-operative
patients. The second outbreak occurred during autumn in a 23-bed stroke
rehabilitation ward. Both wards have a mixture of rooms containing one to four
beds and both have shared bathroom facilities.
Case definition
A case was defined by the sudden onset of vomiting, with or without diarrhoea.
Other symptoms could include nausea, abdominal cramps, myalgia, headache, chills
and fever. The person presenting with signs and symptoms of illness had to have
been in contact with cases or in the environment/geographic area in which the
outbreak was occurring.
Laboratory
methods Faecal specimens were collected and sent to the Institute of
Environmental Science and Research Limited for identification of NV by reverse
transcriptase polymerase chain reaction. This technology provides more rapid
identification of a virus in faecal specimens than previous methods. Specimens
were also examined for Clostridium
difficile enterotoxin,
Rotavirus,
Shigella,
Salmonella and
Campylobacter species.
Faecal specimens were collected if a patient had
symptoms that met the case definition. Once NV had been identified in an
outbreak, further faecal specimens were not required and patients were diagnosed
on clinical grounds, providing they met the case definition.
A register was kept in each ward and filled in by staff
or the infection control nurse.
ResultsOutbreak
1 Outbreak 1 lasted 14 days with the first case presenting on 25 July
2000 and the last case developing symptoms on 7 August 2000. The infection
control nurse and the public health service were notified on 27 July after five
cases had developed in the preceding 12 hours during the late afternoon and
night. On investigation, one patient and two staff members had also succumbed
over the previous 48 hours. No precautions had been put in place and by the end
of 27 July a total of 14 cases had presented. Contact precautions were
commenced, staffing guidelines (Table 1) instituted and the ward was closed for
11 days.
Table 1. Staffing guidelines for use during outbreak of
acute gastroenteritis
Forty one cases met the case definition, with 16 patients
and 25 staff affected (Figure 1).
Figure 1. Timeline of symptom duration in Norovirus
outbreak 1
 The attack rate was 57.1% for patients and 41% for staff.
The average age of the patients was 79.5 years (range 65–93). The mean
duration of sickness was 2.2 days for patients and 1.2 days for staff. Three
cases relapsed. One patient died, with gastroenteritis the precipitating event
of his final illness. Seven of nine faeces samples collected from patients were
positive for NV and the other two were negative. Three of the positive NV cases
were also positive for Clostridium
difficile enterotoxin. Once the virus was isolated, no further samples
were sent for virus identification and all following cases were diagnosed on the
case definition and clinical history. As there were no cases identified outside
of the affected ward, a food-borne source from the hospital kitchen was
considered unlikely.
Modified staffing restrictions were commenced immediately
for staff meeting the case definition. A strict staffing regime as suggested by
Chadwick,2 as per Table 1, was developed and
enforced from Day 5 of the outbreak. During the early days of the outbreak there
was not full awareness of both the highly infectious nature of the virus and the
importance of rigorous cleaning followed by disinfection. For example, a commode
containing diarrhoea from a patient who met the case definition was knocked over
in a four-bed room and the area was not disinfected nor the carpet steam
cleaned. It was 72 hours before definitive cleaning action was taken.
After the outbreak ended, an NV education series was
conducted throughout the hospital discussing the case definition, control of
spread, staffing issues, patient and staff outcomes, and the lessons
learned.
Outbreak 2 Outbreak
2 lasted for 16 days from 6 March 2002 to 20 March 2002. Ward staff instituted
infection control precautions immediately on suspicion of gastroenteritis as
soon as a third case was noted early on 8 March. The infection control nurse was
contacted immediately. The ward was closed on 8 March as more cases developed
over the day and the public health service was notified. The ward was closed
from that date for a total of six days. On the date of reopening there had been
no new cases for 24 hours. Three further cases developed after reopening but
cross infection could be contained by contact precautions. Twenty four cases met
the case definition, with 13 patients and 11 staff affected (Figure 2). The
attack rate was 56.5% for patients and 18% for staff. The average age of the
patients was 72.3 years (range 65–86). The mean duration of sickness was
2.5 days for patients and 3.5 days for staff. There were no deaths on the ward
during this time period. Four of five faecal specimens from symptomatic patients
were positive for NV. No other causative organisms were identified.
Several amended measures were used in this outbreak to
contain the infection (Table 2). Staffing restrictions as per Table 1 were put
in place immediately with strong support from management. Paid sick leave over
and above normal sick leave was made available for permanent staff to encourage
compliance with the 48-hour recommendation. The cleaning service was involved
immediately and a rigorous cleaning regime put in place. Strict cleaning and
disinfection were undertaken for any room contaminated by patient vomit or
diarrhoea. Patients remained on the ward for their rehabilitation therapy rather
than attending other therapy areas. Intensive promotion of the importance of
hand hygiene was performed on the ward to educate staff, patients and visitors.
This was backed up by the ready availability of alcohol-based hand gels for all
to use.
Figure 2. Timeline of symptom duration in Norovirus
outbreak 2
 Table 2. Precautions for any outbreak of vomiting and
diarrhoea
DiscussionNV outbreaks are characterised by a
high attack rate of the virus and rapid spread to both patients and staff. We
have shown in this report that the impact of hospital-acquired NV
gastroenteritis can be limited through a strict programme of infection control
measures and ward closure (Table 2). By using the case definition, staffing
guidelines and infection control measures that were developed during the first
outbreak, we were able to implement this programme sooner and more effectively
in the second outbreak. This resulted in a shorter duration of ward closure and
lower staff attack rate. These differences were seen despite the outbreak
duration and patient attack rate being similar. The fact that the staff reported
a longer duration of illness suggests that the staffing restrictions on
returning to work were more strictly adhered to during this episode as opposed
to the first outbreak. It is difficult to enforce sick leave for nursing staff,
particularly casual or bureau staff who do not receive sick
pay.3 This was acknowledged in the second
outbreak with the introduction of special paid sick leave for permanent staff,
which encouraged staff to comply with the guidelines.
Rapid recognition and notification of a gastroenteritis
outbreak is important. While it can be difficult on a geriatric ward to
distinguish an outbreak of gastroenteritis from other causes of diarrhoea and
vomiting it is important to maintain vigilance when several patients present at
once. Delay in instituting control measures can significantly extend the
duration of an outbreak.4 In both outbreaks
there was a delay of 48 hours before the infection control nurse was notified;
however, the index of suspicion was much higher in the second outbreak and
infection control measures were put in place by the ward staff
immediately.
Close liaison between management and staff allowed us to
close the affected wards to new admissions and restrict staff movements.
Requiring staff to stay away until 48 hours after their last symptom was a
contentious issue. The infection control nurse worked closely between nursing
coordinators, unit managers and individual staff members to ensure adherence to
required staff restrictions as per Table 1. Ward closure can be difficult to
achieve if the need for beds is high, such as in acute hospitals or in winter
when beds are in short supply. We believe both ward closure and staffing
restrictions were essential aspects of managing the outbreaks and allowed us to
prevent the spread of infection to other areas, thereby avoiding hospital-wide
disruption.
Recent reports show just how severely hospitals can be
affected if an outbreak is not contained. In 2002 the Victoria Infirmary in
Glasgow was forced to close to admissions for a week after almost 300 patients
and staff were affected.5 Nine other Scottish
hospitals had temporary ward closures. An outbreak in England in 1994 closed a
220-bed hospital due to staff shortages.6 The
costs of staff sickness, bed closures and control measures can be significant.
An outbreak in 1995 in Australia caused closure of several wards for up to 22
days and resulted in estimated costs of AU$7600 for sick leave and AU$10 600 for
bed closures.7 Early closure is likely to
result in an overall net gain, with the initial bed shortages being compensated
for by lower overall disruption.
Evidence-based, clear and workable clinical infection
control systems can prevent the spread of an outbreak. Prompt identification of
a cluster of patients with unexplained vomiting and diarrhoea and immediate
implementation of contact precautions are essential. Involvement of the cleaning
service from the outset is also important, as is educating nursing staff to
clean and disinfect after any environmental contamination. Limiting the movement
of patients from the outbreak ward and tight controls on where the symptomatic
patients are placed, or moved to, within the ward are also vitally important. In
both outbreaks, if a patient met the case definition and was in a four-bed room,
the entire room was placed under contact precautions. Only in the later stages
of the outbreak were infected patients moved to either single rooms or grouped
together. This was to facilitate the re-opening of wards and was decided in
close liaison with the infection control nurse and the clinical staff. Our team
also found that constant feedback, up-to-date information and sharing of the
attached timelines (Figures 1 and 2) assisted staff to comply with precautions
put in place.
A significant proportion of reported outbreaks of NV in New
Zealand occur in healthcare settings,1 and the
greatest burden of illness is seen in the institutionalised
elderly.8 The key points to managing and
limiting an outbreak of this kind include early recognition and notification,
prompt implementation of infection control measures, education of staff,
patients and visitors, staffing restrictions and ward closures.
Author information:
Sarah J Lynn, Senior Registrar, Older Persons’ Health, The Princess
Margaret Hospital, Christchurch; Julianne M Toop, Infection Control
Practitioner, Southern Community Laboratories, Christchurch; H Carl Hanger,
Physician/Geriatrician; Nigel D Millar, Clinical Director, Older Persons’
Health, The Princess Margaret Hospital, Christchurch
Correspondence: Dr
Carl Hanger, Older Persons’ Health, The Princess Margaret Hospital, PO Box
800, Christchurch. Fax: (03) 337 7823; email: carl.hanger@cdhb.govt.nz
References:
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| | Current
issue | Search journal |
Archived issues | Classifieds
| Hotline (free ads) Subscribe | Contribute | Advertise | Contact Us | Copyright | Other Journals |
|