Table 1. Characteristics of Cases Involved in a Norovirus Outbreak Among Residents of an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
Characteristics Total Subjects N=36 (%)
Residents, (%)* 26 (18.2)
Staff, (%) † 10 (3.9)
Age, years
Mean (SD) 75.0 (18.0)
Median 82.0
Range 36‐96
Gender, %
Female 72.2
Male 8.3
Disease onset, dates (range) February 19‐March 14
Disease duration, days
Figure 1. Epidemic Curve of Disease Onset by Day in a Norovirus Outbreak (N=36) Among Residents of an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
0 1 2 3 4 5 6 7 8
Number of Cases
Norovirus Outbreak Among Residents of an Assisted Living Facility, Houston County, Alabama 2010 (AL1003NRV35a)
Introduction
On March 9, 2010, Public Health Area (PHA) 10 surveillance nurse contacted the Alabama Department of Public Health (ADPH) Surveillance Branch, concerning a gastrointestinal (GI) outbreak of unknown origin at an assisted living facility in Houston County. Facility staff notified the surveillance nurse of an outbreak that had been in progress for 2‐3 weeks, affecting both residents and employees.
Methods
On March 9, the facility reported 26 residents and 10 employees ill with symptoms of nausea, vomiting, diarrhea, and fever. The facility had a total of 143 residents and 259 employees. The surveillance nurse conducted an onsite visit; no environmental assessment was conducted. The facility is a one‐leveled structure with multiple wings, where two residents share each room (Appendix 1).
In addition, the surveillance nurse collected information of symptoms and disease duration developed a map of the ill residents by disease onset date and room location to depict the extent of the outbreak (Appendix 2).
Three stool specimens were tested for the presence of Escherichia coli, Clostridium difficile, and rotavirus at clinical laboratories, with negative results. Two of these specimens underwent further testing for norovirus at the state laboratory (BCL).
The case definition included residents and employees with GI symptoms between February 19 and March 14.
Results
A total of 26 (18.2%) residents and 10 (3.9%) staff members reported GI symptoms. The mean age of the ill subjects was 75 years, and 26 (72%) were female. The mean disease duration was 1.9 days (range 0.5‐5.0 days, Table 1). Figure 1 depicts the epidemic curve of disease onset by date, showing the potential index case on February 19 followed by a gap of 13 days, after which additional residents and employees became ill. The most common symptom was diarrhea (Table 2). BCL confirmed the presence of norovirus in two stool specimens submitted from this outbreak (Appendix 3).
Table 2. Frequency of Symptoms Presented by Cases (N=36) Involved in a Norovirus Outbreak Among Residents of an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
Symptoms Yes (%)
Diarrhea 34 (94.4)
Vomiting 23 (63.9)
Cramps 19 (52.8)
Myalgia 8 (22.2)
Headache 7 (19.4)
Fever 4 (11.1)
Chills 3 (8.3)
Discussion/ Conclusion
Prior to February 19, a resident from another assisted living facility experiencing an outbreak of norovirus was transferred to this facility. At that time, the facility did not know the transfer was coming from a place facing a norovirus outbreak. On February 19, the transferred resident started exhibiting symptoms of an apparent viral infection which lasted for five days (February 19‐24). By March 4, other residents and staff at the facility began exhibiting similar GI illness. Despite the 13 day gap between the potential index case and subsequent illnesses, it is possible that ongoing person‐to‐person transmission occurred via asymptomatic residents and employees.
During the analysis of the data, some limitations were observed
because information was limited to symptoms recorded on the Gastrointestinal Case Log. The facility did not notify ADPH until three weeks into the outbreak and a standardized questionnaire was not available to investigate the problem. As a result, epidemiologic information was limited to ill patients (i.e., no control group was available for comparison). Finally, an environmental inspection was not conducted.
Norovirus is a group of highly contagious viruses that cause acute gastroenteritis in humans. The incubation period for norovirus infection is usually 24‐48 hours, but symptoms can appear within 12 hours of exposure. In addition, 30% of infections may be asymptomatic. Norovirus transmission is primarily through the fecal‐oral route (contaminated food and water) or by direct person‐to‐person contact. During outbreaks, it is common for more than one mode of transmission to occur. There is no specific therapy for viral gastroenteritis and treatment consists of administering fluids to avoid dehydration. However, guidelines are available to aid in containing outbreaks and preventing further spread. The surveillance nurse consulted central office staff and provided the following norovirus specific recommendations to the facility:
Distributed the Centers for Disease Control and Prevention Norovirus Fact Sheet and emphasized hand washing (Appendix 4).
Discouraged usage of hand sanitizers until outbreak resolves as they are not effective against norovirus.
Advised to record the names, illness onset dates, symptoms, and room locations of ill and/or hospitalized residents and employees on Gastrointestinal Case (Appendix 2).
Advised to cancel all group activities and avoid transporting patients unless due to an emergency.
Advised to assign employees to specific work areas and send symptomatic staff members home immediately, requiring staff to be symptom free for two days prior to returning to work (three days if preparing food).
Requested stool specimens for symptomatic residents sent to BCL for testing and provided information, specimen containers, and lab forms for specimen collection and shipping.
Advised to contact the local nurse to report any additional illness.
In addition, the following control measures were already implemented by the facility prior to ADPH’s investigation:
Disinfected all common areas, doorknobs and bathrooms with Clorox® and Lysol®. All common linens
Sanitized all dishes, serving utensils, and condiment containers daily.
All freezer and refrigerator items checked to insure proper dates.
Notified family members of an outgoing outbreak.
Posted restricted visitor signs and limited visits.
Advised staff to use gloves and good hand washing.
Closed the central dining area and delivered meals via tray to rooms.
Served meals using paper products.
In conclusion, a norovirus outbreak occurred among residents and employees of an assisted living facility in Houston County. Norovirus transmission likely occurred from person‐to‐person and affected at least 36 of 402 potentially exposed residents and employees. The ADPH PHA 10 surveillance nurse conducted an on‐site assessment and provided recommendations to control the outbreak.
Appendices
Appendix 1: Facility Map With Locations of Ill Residents
Appendix 2: Gastrointestinal Case Log
Appendix 3: Laboratory Report
Appendix 4. Centers for Disease Control and Prevention Norovirus Fact Sheet
Appendix 1. Facility Map With Locations of Ill Residents Involved in a Norovirus Outbreak Among Residents at an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
Appendix 2. Gastrointestinal Case Log Utilized During a Norovirus Outbreak Among Residents at an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
Appendix 3. Laboratory Report of a Clinical Specimen Obtained During an Outbreak of Norovirus Among Residents at an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
Appendix 4. Centers for Disease Control and Prevention Norovirus Fact Sheet Provided During a Norovirus Outbreak Among at an Assisted Living Facility in Houston County, Alabama – March 2010 (AL1003NRV‐35a).
