Canada Communicable Disease Report

1 April 2008

Volume 34

Number 04

Outbreak of norovirus gastroenteritis at a university student residence – Edmonton, Alberta, 2006

L Honish, MSc (1), J Talbot, MD, FRCPC (1), D Dragon, PhD (2), D Utgoff (2)

1. Capital Health-Public Health Division, Edmonton, Alberta
2. University of Alberta, Edmonton, Alberta

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

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.