Outbreak of norovirus gastroenteritis at a university student residence - Edmonton, ALBERTA, 2006

22.may.08
Public Health Agency of Canada
L Honish, MSc, J Talbot, MD, D Dragon, PhD, D Utgoff

Introduction
On 27 September 2006 Capital Health-Public Health Division (CHPHD), which serves
Edmonton, Alberta and its surrounding communities, was advised by the student health
centre of a local university that several students living in the main campus
residence had experienced onset of gastrointestinal illness in the previous several
days. CHPHD initiated an outbreak investigation based on this information.
Methods
The affected university had an approximate enrolment of 35,000 students at the time
of the outbreak. The main residence, with approximately 1,800 residents, consisted
of four interconnected buildings and an onsite food facility. CHPHD requested that
university personnel perform the following to assist in managing and controlling the
outbreak:
* Develop a system through which it could be determined how many students in the
residence had experienced new onset of vomiting and/or diarrhea retrospectively
(during the month of September 2006) and prospectively (students with new onset each
24 hour period during the investigation),
* Post a CHPHD notice to students and visitors throughout the residence. The notice
included information regarding the outbreak and public health recommendations
(report new onset of vomiting and/or diarrhea to a residence coordinator, remain in
room as much as possible while ill, postpone visits to ill residents, and frequent
hand washing),
* Conduct daily enhanced environmental cleaning of "high touch" surfaces in the
residence (procedures were modified from CHPHD nursing home outbreak management
guidelines)(1),
* Remove self-service open food and utensil displays in the common dining area
during the outbreak,
* Seek symptomatic student volunteers to provide stool specimens, and
* Provide daily status reports to CHPHD for the duration of the outbreak.
University administration created an emergency operations centre (EOC) to facilitate
the management of the outbreak. Residence floor coordinators were deployed to assist
with case finding, through daily canvassing of all student residents in each area of
the facility. Waterless hand wash agent dispensers were made available throughout
residence. Daily teleconferences were held between the EOC and CHPHD investigators.
The residence living areas and food facility were inspected by CHPHD environmental
health officers (EHOs); additional outbreak management recommendations developed
from inspection findings were provided to university officials. Stool specimens were
submitted to the Provincial Public Health Laboratory for analysis (including
norovirus RT-PCR). The outbreak period was defined through examination of
gastrointestinal illness surveillance information provided by university officials,
and the surveillance information was used for estimation of when incidence returned
to baseline (see Discussion).
Results
Case series. The case definition for this outbreak was restricted to residents of
the main student residence of the affected university between 1 September and 10
October, 2006 that reported onset of vomiting and/or diarrhea. A total of 139
individuals met this definition (the epidemic curve is shown in Figure 1). Most
cases had onset during the period 20 September and 7 October.
Figure 1: Epidemic curve, outbreak of norovirus gastroenteritis at a university
student residence - Edmonton, Alberta, 2006
Figure 1: Epidemic curve, outbreak of norovirus gastroenteritis at a university
student residence - Edmonton, Alberta, 2006
Cases reported symptoms of vomiting (37%), diarrhea (18%), or vomiting and diarrhea
(34%). Mean and median duration of illness was 2.0 days. No hospitalizations were
reported among outbreak cases. Cases were reported in each of the four main
residence buildings, with a range of 19 to 44 cases per building. Most students at
the affected university lived in off-campus housing in a metropolitan area of more
than one million residents, and were considered a separate population for the
purposes of outbreak investigation and control.
Stool specimen results. Two stool specimens were collected from outbreak cases, both
of which were positive for norovirus. As per CHPHD protocol, no further specimens
were collected and subsequent cases were defined by the clinical case definition.
Source investigation and control. The investigation considered food, water and
person-to-person transmission as the source of the outbreak:
* No food exposures were identified as a possible source. There were no food
handling deficiencies observed in the onsite food facility during the investigation.
Exclusion policies for foodservice workers who may have been suffering
gastrointestinal illness were reaffirmed. Informational posters were provided to
remind workers to report illnesses to their employers and to not work while ill.
* No common resident social activities were identified that could explain the outbreak.
* The drinking water supply for the facility was not unique; all drinking water for
the residence originates from the municipal water utility.
* The congregate living areas were investigated. Dwelling rooms were single or
double occupancy. Most residents used shared washroom facilities (usually, one set
per floor), and each floor typically also had a shared food preparation and laundry
area. Soap and single service towelling dispensers or hand dryers were sometimes not
in close proximity to sinks (washrooms), or were not made available (food
preparation areas), as residents were expected to provide their own washing
supplies. University officials ensured that hand washing supplies were made
available at appropriate proximity to sinks as recommended by CHPHD. Laundry areas
(available on each floor of the residence) were in close proximity to food
preparation areas. Recommendations were provided to students regarding handling of
their laundry i.e. laundry should be taken directly to the laundry area in bags if
possible, then carefully placed into the washing machine with as little
agitation/shaking as possible, after which hands should be washed.
Discussion
Outbreaks of norovirus gastroenteritis have been reportedly previously on college
campuses(2-4), including an outbreak at another Canadian university campus(5) that
occurred concurrently with the Edmonton outbreak. These are likely the result of
conditions on campuses that are conducive to norovirus transmission, including close
living quarters, shared bathrooms and common areas, large food service facilities
where food is often self served, and person-to-person contact through sports and
recreational activities(6). Norovirus outbreaks are also frequently observed in
other congregate living settings such as nursing homes, cruise ships and emergency
shelters(7).
A challenge for the investigation was establishing the beginning and end of the
outbreak - there was limited prior surveillance of gastrointestinal illness among
those living in student residence. On 20 September case numbers were clearly
deviating from baseline gastrointestinal illness reports from residents. No
representative clinical specimens could be collected from these early cases;
etiology could only be assigned to cases that occurred during the investigation.
There was a return to lower incidence levels by 7 October.
No precipitating event of relevance for the outbreak (e.g. illness in a food
handler, social activity among residents) was identified. A point source by itself
does not explain a norovirus outbreak of this duration. Consumption of food prepared
at the residence food facility was an exposure common to outbreak cases and is a
possible source if handled by norovirus-infected employees; however, there were no
reports of gastrointestinal illness among residence food facility employees in the
days prior to the start of the acute phase of the outbreak. There is no evidence to
suggest that contaminated drinking water was an outbreak source. The outbreak may
have been propagated by contact with environmental surfaces in the residence
contaminated by infected students. Suboptimal availability of hand washing supplies
in close proximity to sinks in common washroom, food preparation and laundry areas
may have increased the likelihood of such transmission. A reduction in
gastrointestinal illness incidence after implementation of contact precautions is
supportive of person-to-person transmission being an important factor in this
outbreak.
Key in managing the outbreak was prompt reporting of increased incidence of
gastrointestinal illness by the university's student health centre to the local
public health department, and exemplary collaboration between public health and
university officials in the development and rapid implementation of outbreak
management recommendations. University administration created the EOC based on a
model developed through pandemic influenza response planning, to facilitate the
management of the outbreak. The use of an EOC by the university contributed to
efficient communication of critical outbreak management information and effective
onsite planning and response to the evolving outbreak situation and associated
concerns of residence inhabitants.
Conclusions and Recommendations
Learning institutions should consider the following recommendations to prevent,
control and manage potential outbreaks in student residences:
* Ensure that appropriate hand washing supplies are available in close proximity to
sinks in common washroom facilities and food preparation areas in residences;
* Develop timely syndromic surveillance systems for populations living in student
residences (possibly facilitated through campus student health centres). To
facilitate early detection of outbreaks of two infectious diseases common among
those in congregate living settings (i.e. influenza and norovirus), surveillance
information collected should include (but not necessarily be limited to) date of
initial onset for new cases of fever and new cough, or, vomiting and/or diarrhea;
* Assess common food preparation and dining areas for norovirus transmission risks
and mitigate these risks where possible;
* Report promptly any suspected outbreaks to the local public health department;
* Form an emergency operations centre to assist in managing identified outbreaks.
Acknowledgements
The authors thank the following for their assistance:
C. Webb, P. Phan, R. Reive, R. Gibson, Capital Health-Public Health Division,
Edmonton, Alberta; Dr. R. Rennie, Provincial Laboratory for Public Health
(Microbiology), Edmonton, Alberta; O. Yonge, R. Richards, University of Alberta,
Edmonton.
References
1. Capital Health-Public Health Division. Outbreak prevention, control and
management in continuing care centres, 2006-2007. Edmonton: Capital Health, 2006.
2. Kilgore PE, Belay ED, Hamlin DM et al. A university outbreak of gastroenteritis
due to a small round-structured virus. Application of molecular diagnostics to
identify the etiologic agent and patterns of transmission. J Infect Dis
1996;173:787-93.
3. Centers for Disease Control and Prevention (CDC). University outbreak of
calicivirus infection mistakenly attributed to Shiga toxin-producing Escherichia
coli O157:H7 - Virginia, 2000. MMWR 2001;50:489-91.
4. Daniels NA, Bergmire-Sweat DA, Schwab KJ. A foodborne outbreak of gastroenteritis
associated with Norwalk-like viruses: First molecular traceback to deli sandwiches
contaminated during preparation. J Infect Dis 2000;181:1467-70.
5. Public Health Agency of Canada. Norwalk-type virus: New Brunswick. Infectious
Diseases News Brief - October 20, 2006. Ottawa: Public Health Agency of Canada.
Available at http://www.phac-aspc.gc.ca/bid-bmi/dsd-dsm/nb-ab/2006/nb4206-eng.php.
Date of access: 5 November 2007.
6. Moe CL, Christmas WA, Echols LJ. Outbreaks of acute gastroenteritis associated
with Norwalk-like viruses in campus settings. J Am Coll Health 2001;50:57-66.
7. Estes MK, Prasad BV, Atmar RL. Noroviruses everywhere: Has something changed?
Curr Opin Infect Dis 2006;19:467-74.