As new strains strike, brace for norovirus outbreaks that can sicken staff, patients

Canadians offer valuable insights into fighting an outbreak

Cruise ships have become notorious for norovirus outbreaks that ruin passengers' exotic vacations. But as two new strains sweep the country, norovirus wields the greatest punch against long-term care facilities and hospitals, where outbreaks afflict patients and employees and lead to absenteeism and staff shortages.

More than 1,300 norovirus outbreaks occurred nationwide in the fall of 2006. While half of them were in long-term care facilities, a significant number occurred in hospitals, the Centers for Disease Control and Prevention in Atlanta reported. For example, in New York state, 26 (8%) of 333 outbreaks of acute gastroenteritis occurred in hospitals. In North Carolina, health authorities confirmed that norovirus was the cause of death of a 90-year-old nursing home patient last year. That is the first time the virus has been directly identified as a cause of death in the United States.1

Norovirus outbreaks are likely to increase this fall and winter, as well, as part of a seasonal trend, says Jacqueline Tate, PhD, an officer with CDC's Epidemiologic Intelligence Service. With new strains, the transmissibility will be even greater than usual, she says. "There can be high attack rates associated with norovirus because it has such a low infectious dose," she says.

In 2008, norovirus surveillance will increase as it becomes reportable through the National Outbreak Reporting System. Norovirus has an incubation period of just 12-48 hours and is characterized by vomiting, diarrhea, abdominal cramping and nausea. To limit transmission, CDC recommends strict adherence to infection control and environmental decontamination.

Preventing the spread of norovirus infection

The Centers for Disease Control and Prevention provides the following guidance to health care facilities seeking to control a norovirus outbreak:

  • Isolation precautions: Patients with suspected norovirus infection should be managed with standard precautions with careful attention to hand hygiene practices. However, contact precautions should be used when caring for diapered or incontinent persons, during outbreaks in a facility, and when there is the possibility of splashes that might lead to contamination of clothing. Persons cleaning areas heavily contaminated with vomitus or feces should wear surgical masks as well. In an outbreak setting, it may be prudent to place patients with suspected norovirus in private rooms or to cohort such patients.
  • Environmental disinfection: CDC recommends either chlorine bleach or U.S. Environmental Protection Agency (EPA) approved disinfectants for use in controlling norovirus outbreaks. All disinfectants should be used on clean surfaces for maximum performance. Please see the U.S. Environmental Protection Agency (EPA) web site ( for a list of hospital disinfectants registered by the EPA with specific claims for activity against noroviruses. It should be noted that evidence for efficacy of disinfectants against norovirus are usually based on data of efficacy against feline calicivirus (FCV) as a surrogate for norovirus. However, feline calicivirus (a virus of the respiratory system in cats) has different physio-chemical properties to norovirus and there is debate on how well data on inactivation of FCV reflect efficacy against norovirus.
    • Chlorine bleach should be applied to hard, nonporous, environmental surfaces at a minimum concentration of 1,000 ppm (generally a dilution 1 part household bleach solution to 50 parts water) This concentration has been demonstrated in the laboratory to be effective against surrogate viruses with properties similar to those of norovirus. Health care facility staff should use appropriate PPE (e.g., gloves and goggles) when working with bleach. In areas with high levels of soiling and resistant surfaces, up to 5,000 ppm chlorine bleach may be used.
    • EPA-approved disinfectants should be used according to manufacturers' instructions.
    • Quaternary ammonium compounds are often used for sanitizing food preparation surfaces or disinfecting large surfaces (e.g., countertops and floors). However, because noroviruses are nonenveloped virus particles, most quaternary ammonium compounds (which act by disrupting viral envelopes) do not have significant activity against them.
    • Phenolic-based disinfectants have been shown to be active against noroviruses in the laboratory. However, this activity may require concentrations two- to fourfold higher than manufacturer recommendations for routine use.
    • Heat disinfection [i.e., pasteurization to 60°C (140°F)] has been suggested, and used successfully under laboratory conditions, for items that cannot be subjected to chemical disinfectants such as chlorine bleach.

Additional measures:

  • Avoid sharing staff members between units or facilities with affected patients and units or facilities that are not affected.
  • Group symptomatic patients and provide separate toilet facilities for ill and well persons.
  • Instruct visitors on appropriate hand hygiene and monitor compliance with contact isolation precautions.
  • Close affected units to new admissions and transfers.

(Editor's note: A CDC fact sheet on norovirus in health care facilities is available at

Although norovirus is not usually life-threatening, hospital outbreaks are disruptive and even debilitating. Royal University Hospital in the Saskatoon Health Region in Canada weathered a norovirus outbreak last winter, which sickened 34 patients, 88 employees, and 16 physicians. The health region now shares its "lessons learned" from the 2006 outbreak with other hospitals.

Saskatoon Health Region has used the experience to improve its overall response plan for infectious diseases, but it also is bracing for the possibility of another norovirus outbreak. "Plan ahead because outbreaks can strike at any time," advises Donna Wiens, RN, BN, CIC, regional manager for infection prevention and control.

Hospital sets up Incident Command System

As it usually does, the norovirus outbreak in Saskatoon began in the community. Most likely the first patient came to the emergency room with severe gastroenterological symptoms and was admitted.

"We had reports from a unit saying, 'We're seeing vomiting and diarrhea in [several] patients. Please come and investigate,'" recalls Wiens.

Soon it became clear that there had been other, unrecognized cases. Some employees already had gotten ill. "Often, once you investigate, [you realize] the situation is bigger than you realize," she says. "Reports started coming from other units saying, 'We have this problem, too.' We had at least four units that had confirmed cases of norovirus during that same outbreak period."

Within a couple of days, the health region decided to convene an Incident Command System, which brought together a team that included managers, infection control, employee health, and public health. The team met each day — or sometimes twice a day — to review the cases and strategies to stop transmission.

The outbreaks cannot be controlled without taking stringent measures to prevent transmission, says Wiens. Norovirus "may be self-limiting in an individual. You get sick and you get better. But it's very transmissible. We know that people can get sick more than once. The immunity is very short. Outbreaks are not quickly self-limiting.

"I've seen outbreaks poorly controlled that went on for six weeks or more. They just keep recirculating in a population," she says.

While the health region focused on infection control, the command team provided feedback and communication to the staff as well as the public through regular press releases, pamphlets, and daily updates to employees. "You have to work closely with staff to get their buy-in and get the best result possible," says Jean Morrison, RN, MN, MHSA, chief nursing officer and vice president, performance excellence.

Combating the outbreak

To control the outbreak, the health region implemented a number of measures at Royal University Hospital:

  • Employee health monitored employee illnesses and sent staff home, as necessary. Health care workers can have too much dedication to their jobs. "That was one of our challenges. Staff felt they needed to come to work even if they didn't feel well, and they got sick at work," says Morrison. Employee health tracked the cases of staff illness — and made sure that employees stayed home for 48 hours after the symptoms resolved, as recommended by CDC.
  • Staff could not "float" among units. Staff were restricted from moving from a unit with norovirus cases to one that was unaffected. However, staff who served multiple units, such as radiology technicians, and physicians still needed to visit the affected areas.
  • Some units were closed to new admissions or transfers. The hospital was able to direct patients to acute care beds in other units. In some cases, however, surgeries were delayed or rescheduled.
  • Visitors were restricted from entering affected units. Exceptions were made for the family members of patients who were terminally ill or, in some cases, for the primary caregivers of some patients.
  • Environmental surfaces, including door handles, railing, taps, counters, equipment, were cleaned thoroughly. The hospital switched to an accelerated hydrogen peroxide-based cleaner and became more aggressive about cleaning surfaces.
  • Employees did not wear their uniforms outside the hospital. After every shift, employees changed their shoes and put their uniforms in a bag to wash them. "We wanted to decrease any chance we were sending infections back to the community," says Morrison.

After the outbreak subsided, Saskatoon Health Region reviewed its policies and decided to make some changes. To reduce the risk of hand contamination, employees were required to remove artificial nails. Their fingernails must be clipped short and polish-free.

The hospital also is encouraging employees to change out of their uniforms at the end of a shift and not wear them home. New lockers are being installed to give employees a place to store their street clothes.

Meanwhile, the hospital also learned that individual units need the flexibility to make decisions that suit their needs. To enable that, the hospital is creating unit-specific response plans that allow staff to have input when an infectious disease emerges or some other disaster occurs. "We will be putting together a template to make decisions and act at the unit level," says Morrison.


1. Centers for Disease Control and Prevention. Norovirus activity — United States, 2006-2007. MMWR 2007; 56:842-846.