By Mary M. McFadden, RN, MHA, CIC, CHS, and Beth Christy, MT, MSHA, CIC
According to the Centers for Disease Control and Prevention (CDC), each year norovirus causes more than 2.1 million cases of acute gastroenteritis and results in over 70,000 hospitalizations and over 800 deaths, mostly among children and the elderly. It is most common in winter months, although it can infect exposed people at anytime.
Norovirus was previously known as Norwalk virus and the cause of significant gastroenteritis. It was first detected in stool samples from young children in an outbreak in Norwalk, Ohio in 1968.(1) Since that time, it has been indentified in many other outbreaks. After being identified as the cause of gastrointestinal outbreaks on cruise ships, the name was shortened to norovirus and approved by the International Committee on Taxonomy of Viruses in 2002.(2)
The virus is a single stranded RNA, non-enveloped virus in the Caliciviridae family. Transmission occurs by ingestion of fecally contaminated food or water, person to person contact and from contaminated surfaces.(3) Additionally, inhalation of infected vomitus is an additional mode of transmission.(3) Affecting people of all ages and at a low dose infectivity of <20 viral particles, it is the most contagious infection known, with high infectivity rates.(4)
Healthcare facilities that experience outbreaks of norovirus are challenged with disinfection methods, case histories and control measures. Because the norovirus is highly contagious and lives in the inanimate environment, isolation and cleaning practices must be vigilant. Patients should be isolated in single room until they have negative lab results. Although norovirus affects patients who are immunocompromised, including pediatrics, there is little data available on how to manage this population. For example, data is not available as to how long they may shed the virus after the resolution of symptoms and therefore how long they should remain on contact isolation. In addition, healthcare workers must be monitored for signs and symptoms of the virus and visitors kept to a minimum and are virus free.(4)
Description of Event and Interventions
In the early months of 2012, an outbreak of norovirus began in our Pediatric Transplant Unit. The population on this unit consists primarily of multi-visceral or multi-organ transplant patients who are especially vulnerable to a norovirus infection. In fact, norovirus PCR testing is a component of a battery of tests for patients that develop diarrhea on this unit. From January to April 2012, there were 15 cases of Norovirus enteritis on the unit, seven of which were healthcare acquired. In addition, nine out of the 25 nurses caring for patients exhibited norovirus like symptoms. Over the course of three months, this impacted isolation of patients, patient movement, care providers, and environmental cleaning.
Initially, the infection preventionists developed a case definition for both patients and care providers. A patient was identified as being infected with norovirus if they had signs and symptoms of norovirus (i.e., increased stool or ileostomy output), and had a positive qualitative norovirus, RT-PCR test. The cases were considered health care acquired if the patient had been in the hospital greater than 72 hours when symptoms began, or were readmitted within 24 hours of discharge. The average incubation period for norovirus-associated gastroenteritis is 12 to 48 hours.(5)
The definition for healthcare-acquired gastroenteritis of the care providers was fulfilled if a care provider had one or more of the following symptoms of norovirus (nausea, myalgia, low-grade fever, malaise, headache, acute-onset vomiting, watery and non-bloody diarrhea with abdominal cramps) and had cared for a patient with norovirus within 48 hours of symptom onset. The care providers only included nurses as other disciplines were unable to be tracked during the outbreak.
The first community-acquired case presented in early January which is not unusual. The hospital norovirus outbreak mirrored the peak season in the U.S., and not surprisingly the majority of norovirus cases were community-acquired. The outbreak was likely driven by admission of norovirus-infected patients to the unit. It was hospital policy to place these patients on contact isolation in addition to standard precautions. Signage was placed on the patients door to notify the care providers and family members to wash their hands specifically with soap and water. The room and equipment used by the patient was cleaned with 10 percent bleach and/or commercially prepared bleach wipe.
The first healthcare-acquired case occurred 10 days after the first community-acquired case was admitted. The infection prevention team made specific recommendations to the hospital leadership, physicians and care providers concerning room and unit cleaning, and hand hygiene. Additional interventions had to be implemented when two more cases of healthcare-acquired norovirus were diagnosed in the unit, and the first cases of infected care providers were reported. An increased effort was made to educate the family on hand hygiene and isolation practices. Contact precaution guidelines were reinforced and unnecessary patient travel was restricted. Additional education on cleaning the environment, hand hygiene and symptoms of norovirus was provided to environmental services and care providers. After doing hand hygiene education with care providers, a post test was used to evaluate competencies of care providers on hand hygiene. We also followed the recommendations made by the CDC on furloughing care providers by excluding ill personnel from work for 48 hours after the resolution of symptoms.(5)
Even with these interventions, we continued to see healthcare-acquired norovirus infections. By week eight, we added an environmental services associate (typically there is only one environmental service associate per unit) to ensure the entire unit was cleaned with a 10 percent bleach solution including patient rooms and all high-touch surfaces. Equipment was cleaned witha bleach wipe between each patient. At this point we only allowed essential care providers. Volunteers, pastoral care were prohibited from entering the unit. Child life services were limited to one dedicated person during the outbreak. We also limited visitation to immediate family only. A short informational sheet on norovirus was required to be given to all the families on hand hygiene, limited visitation, and contact precautions.
Despite the aforementioned efforts, another healthcare-acquired norovirus infection was identified. At this point all patients with norovirus were cohorted to one side of the unit and nursing care providers were cohorted to care for only those patients. Environmental services increased decontamination efforts by terminally cleaning patients room and the parents lounge, including the use of a portable UV disinfection system. Additional environmental services associates were added for night cleaning and continuous, thorough cleaning of high-touch surfaces. The cleaning agent was changed from bleach to a hydrogen peroxide based product. This practice continued for two weeks. No further cases were reported after this.
Once the outbreak stopped, the number of associates from EVS returned to baseline; however, we continue to use the hydrogen peroxide based product rather than 10 percent bleach or bleach wipes on this unit. Because of chronic shedding noted in these immunocompromised pre- and post- transplant patients, the patients have continued to be isolated until surveillance RT-PCR for norwalk is negative. All patients with prior norwalk were tested monthly for norovirus during hospitalization and on re-admission to the hospital.
At the end of the outbreak, we believe that adding additional environmental services associates for cleaning and also changing the agent was instrumental in eradicating the outbreak; however, each intervention was equally significant. If this occurs again, we would implement these strategies from the start of another outbreak.
It is difficult to determine whether keeping the patients on isolation until they are negative for norovirus by PCR is really warranted. Prolonged shedding of immunocompromised patients is well documented. However, it is completely unclear if prolonged shedding can cause ongoing transmission. In the norovirus outbreak in HSCT in Germany, stool specimens were positive for norovirus-RNA for a median of 30 days but no transmission was observed once patients were asymptomatic for 48 hours.(6) This needs further investigation especially in an immunocompromised patient population such as this. It is difficult to limit travel and isolation can impact the patient and their family members in a negative manner.
Strict practices including vigilant cleaning methods, hand hygiene, appropriate isolation and education must be implemented immediately upon detection of a questionable outbreak. Every person, including immediate family members, is key to the control and eradication of the virus. Continuous communication and collaboration among all care providers contribute to a safer environment even in high-risk situations.
Mary M. McFadden, RN, MHA, CIC, CHS, is director of infection prevention at MedStar Georgetown University Hospital. Beth Christy, MT, MSHA, CIC, is infection preventionist at MedStar Georgetown University Hospital.
1. Jiang X, Wang M, et al. Sequence and Genomic Organization of Norwalk Virus. Virology, July 1993, 195(1):51-61.
2. ICTVdB Management (2006), The Universal Virus Database, version 4.
3. Said, MA, Perl TM, Sears CL. Healthcare epidemiology: gastrointestinal flu; Norovirus in healthcare and long-term care facilities. CID 47 (9): 1202-8. November 2008.
4. Lopman BA, Reacher MH, Vipond IB, Sarangi J, Brown DW, Clinical manifestation of Norovirus gastroenteritis in healthcare settings. CID, 2004: 39(3):318-324
5. MacCannell, Taranisia, et al. Guideline for the Prevention and Control of Norovirus Gastroenteritis Outbreaks in Healthcare Settings. Centers for Disease Control and Prevention.
6. Schwartz S, et al. Norovirus gastroenteritis causes severe and lethal complications after chemotherapy and hematopoietic stem cell transplantation. Blood. 2011; 117:5850-56.