Guidelines for the Epidemiological Investigation of Gastroenteritis Outbreaks in Long Term Care Facilities

Revised, October, 2001

Single Case Management
Outbreak Management


Outbreaks of gastroenteritis occur in nursing homes and other long term care facilities (LTCFs) each year, most commonly in the winter. Risk factors in these settings include the close proximity of ill residents and staff in close living quarters and the decreased personal hygiene among some residents due to incontinence, immobility, or reduced alertness.

Viruses, such as Norwalk-like agents, are the most common agents causing nursing home outbreaks of gastroenteritis. Viral gastroenteritis is a self-limiting intestinal illness with symptoms of diarrhea and/or vomiting. Additional symptoms may include nausea, abdominal pain, headache, muscle ache, and low grade fever. The incubation period is 12 to 48 hours and gastrointestinal symptoms usually last 12 to 60 hours. The virus is passed from person to person through the fecal-oral route (fecal matter to mouth); contaminated food and water have also been implicated as vehicles for transmission in outbreaks. Additional information can be found in the reference: Centers for Disease Control and Prevention (CDC), Morbidity and Mortality Weekly Report (MMWR), Norwalk-Like Viruses: Public Health Consequences and Outbreak Management. 2001;50 (RR-9).

For LTCF residents, gastroenteritis is important because it can lead to more serious illnesses and complications, such as dehydration, debilitation, hospitalization, and death. The symptoms, course, treatment, and control measures for gastroenteritis outbreaks in a LTCF will vary depending on whether the agent is probably viral or bacterial (such as Salmonella or Shigella).

In order to facilitate investigations of gastroenteritis outbreaks and implementation of control measures, the following guidelines have been established. These guidelines are divided into four sections:

  • Section 1 provides a working case definition and an outbreak definition.
  • Section 2 addresses the use of surveillance to detect cases.
  • Section 3 outlines the management of an individual case of gastroenteritis.
  • Section 4 outlines the management of an outbreak.

Section 1. Definitions

A. Case Definition
A case of gastroenteritis is defined as a person with diarrhea or vomiting. Diarrhea is defined as two or more loose stools per day or an unexplained increase in the number of bowel movements.

B. Outbreak Definition
An outbreak of gastroenteritis is defined as three or more residents from a single ward or unit, or 3% or more of the entire facility, who develop diarrhea and/or vomiting within a 7 day period.

Section 2. Surveillance

Each LTCF should have its designated infection control practitioner (ICP) routinely maintain records on the occurrence of diarrhea and vomiting among all residents and staff. When a person meeting the case definition is identified, the case management procedures described below should be followed. Any employee with gastrointestinal illness should be instructed to report it to Employee Health or the ICP.

Section 3. Single Case Management

Each time a case of gastroenteritis is recognized in a resident or employee, the following measures should be implemented:

A. Residents

  • Restrict the case to his/her room and restrict from participating in group activities for 2 days after the last episode of diarrhea or vomiting.
  • Wear gloves. Direct patient care providers should wear disposable gloves when handling feces or fecally-soiled articles or equipment (e.g., cleaning or changing an incontinent patient, cleaning feces from a bed or bedpan, etc.).
  • Wash hands. Employees and residents must WASH THEIR HANDS carefully after contact with any feces or fecally-soiled material. Employees should wash their hands after removing gloves.
  • Dispose of feces or fecally-soiled material in the sanitary sewer (toilet), or place in plastic bags for disposal as special medical waste.
  • Clean environmental surfaces (toilets, bedpans, fecally-soiled beds, etc.) with cleaning products and procedures normally used by the facility.
  • Practice infection control precautions. Each LTCF should practice the Standard Precautions recommended by the CDC Hospital Infection Control Practices Advisory Committee at all times, regardless of the presence of an outbreak

B. Employees

When a case of gastroenteritis is recognized in an employee, reassign the employee to non-patient care and non-food handling duties or exclude until 2 days after the resolution of diarrhea and/or vomiting. If salmonellosis, shigellosis, or E. coli infection is diagnosed, the local health officer may recommend additional control measures.

Section 4.Outbreak Management

A. Reporting
Code of Maryland Regulations and require LTCFs to report gastroenteritis outbreaks to the local health department within 24 hours. In the event of an outbreak on a weekend or holiday, please contact your local health department for the telephone number used to contact them at those times.

B. Outbreak Control Measures
Control measures for an outbreak of gastroenteritis should focus on stopping person-to-person spread and on removing any ongoing common sources of infection (ill food handler, ill patient care provider, or contaminated food or drink). When an outbreak is identified, the LTCF should institute the following control measures

  • Follow the recommendations for management of individual cases (Section 3, above).
  • Assign employees to care for the same group of patients during a shift if possible.
  • Stop new admissions; readmissions to the facility are allowed, preferably to an unaffected ward.
  • Exclude symptomatic employees from direct patient care and food handling until 2 days after the resolution of diarrhea and/or vomiting.
  • Restrict ill residents from group activities, including group dining, until 2 days after the resolution of diarrhea or vomiting.
  • Institute visitor precautions (e.g., post a sign to alert visitors that an outbreak is occurring and that hand washing is recommended). A visitor ban is not necessary.
  • Wear masks when cleaning areas grossly contaminated by feces or vomitus (since spattering or aerosols of infectious material of viral gastroenteritis may be involved in disease transmission).
  • Handle soiled linen and clothes as little as possible; transport laundry in an enclosed and sanitary manner.

Unless otherwise indicated, all control measures for presumed viral gastroenteritis can be lifted when there are no new cases for 4 days after onset of the last case.

C. Specimen Collection
In all outbreaks of gastroenteritis, specimen collection for bacterial enteric pathogens should be done to rule out Salmonella,Shigella, and E. coli as causative agents. Stool specimens of no more than 10 residents should be collected. Process specimens through a commercial laboratory following their instructions, or use an "enteric pathogen kit" if sending the specimen to the DHMH laboratory. This kit is a jar containing buffered glycerol saline solution. Store and transport at +4 C to the DHMH Laboratories Administration. If Salmonella, Shigella, or E. coli causes the outbreak, the epidemiologic and laboratory investigation will be different from an outbreak presumed to be caused by a virus. In outbreaks of salmonellosis, shigellosis, or E. coli infection additional specimens and questionnaires from food handlers and patient care providers, as well as additional information on residents (e.g., food history) may be needed. The Code of Maryland Regulations also applies (COMAR and .20).

Stool specimen analysis for viral studies is newly available via the DHMH Laboratories Administration. There should be communication with the local health department and the DHMH Division of Outbreak Investigation prior to planning viral studies. When the epidemiology suggests a viral etiology, please refer to the guidelines for the submission of stool samples for viral studies (see Attachment A). Stool samples should be submitted in a sterile stool jar (either the “miscellaneous kit” or the “Norwalk study kit”). DHMH can provide stool collection kits, including stool jars, upon request. All samples should be delivered to the DHMH Laboratories Administration for processing.

D. Data Collection and Summary Report

1. Data Collection
Pertinent information regarding each resident and employee case should be entered into the ICP's surveillance log. This log should be updated daily. Once an outbreak has been identified, cases should be placed on a "line list" (see attached line listing form for gastroenteritis - Attachment B).

2. Epidemic Curve
Plot an epidemic curve ("epi curve") of the resident and employee cases (a graph of the number of cases by date of onset). The epi curve is a useful tool to track the progress of the outbreak and is helpful in determining whether a common foodborne source was present.

3. Summary Report
At the conclusion of the outbreak, the health department investigator and the involved facility should work together to complete a summary report. A copy should be submitted to DHMH. The report may be narrative in format or Attachment C may be completed instead of the narrative report. Regardless of which report format is chosen, please include the epi curve with the report.

E. Local Health Department Responsibilities

Once notified of a gastroenteritis outbreak the local health department should take the following steps:

  • Verify the existence of an outbreak of gastroenteritis by reviewing facility records.
  • Notify DHMH (410-767-6677) of the outbreak.
  • Verify that outbreak control measures have been properly implemented and residents with diarrhea have been cultured to rule out enteric pathogens.
  • Inspect the facility to assess:
  • General cleanliness
  • Availability of soap, towels, running water in rest rooms and in all patient care areas
  • Food preparation areas and food handling procedures when foodborne transmission is suspected
  • Arrange for the collection of data on resident and employee cases as indicated in the line list (Attachment B).

When additional employee information is desired, Attachment D is a standardized questionnaire for investigation of gastrointestinal illness. It can be administered to all or only symptomatic employees at the facility, depending on investigation needs. The questionnaire may be modified as appropriate to the outbreak and facility, duplicated, and distributed as needed.

If the local health department or the LTCF distributes the questionnaire, be sure to fill in the LTCF name (on line 1 on the questionnaire) and the appropriate date for assessing symptoms (on line 10) before duplication.

Download Attachment A (Guidelines)  
Download Attachment B
Download Attachment C
Download Attachment D