New norovirus strain a threat in hospitals

Outbreaks spike, lead to unit closures

A novel strain of norovirus is posing new challenges for hospitals and underscores the importance of vigilant hand hygiene and environmental cleaning.

This winter, norovirus outbreaks have caused unit closures in hospitals in the United Kingdom and Canada and sickened more than a million people in Britain alone. The virus causes more hospital-based outbreaks than any other organism and is the primary culprit in hospital unit closures. It also is the most common cause of foodborne outbreaks. (See related story, below.)

“We have seen a new strain of norovirus emerge that has quickly become the leading cause of outbreaks both here in the U.S. and in other countries,” says Aron J. Hall, DVM, MSPh, epidemiologist with the viral gastroenterology team in the Division of Viral Diseases in the Centers for Disease Control and Prevention in Atlanta. “Any time there is a new strain that emerges there is the chance for an increase in activity, so we’re watching it very closely.”

Norovirus outbreaks typically spike during he winter months, but this year the outbreaks began early. By the end of December, 538 hospital outbreaks had been reported in the UK, according to the Health Protection Agency, a public health organization.

Australia also reported the norovirus cases persisted into the summer months, the HPA said. The new strain has been dubbed Sydney 2012, as it first appeared in Australia in March 2012.

By January, the new strain was having an impact in US hospitals and long-term care centers. In Marin County, CA, for example, an outbreak at a long-term care center sickened dozens of people and contributed to two deaths, according to news reports.

“We have seen plenty of outbreaks reported and some have included some severe outcomes, including deaths,” says Hall, who notes that new strains are sometimes more virulent.

HC outbreaks linked to deaths

Norovirus is a longstanding problem in health care, but public health authorities still struggle to understand its scope. A new surveillance system logged 2,259 acute gastroenteritis outbreaks in 42 states and the District of Columbia in 2009 and 2010. Norovirus was the cause in almost 90% of those with a known etiology.1

CDC has a network of 10 sentinel states that provide information on outbreaks of norovirus and other common pathogens. The surveillance “will hopefully help us determine the magnitude of the season faster than in the past,” Hall says.

Nursing homes are at the greatest risk of norovirus outbreaks. In the 2009-2010 U.S. surveillance, 86% of the norovirus outbreaks occurred in long-term care. About 5% of the outbreaks occurred in hospitals. A study of 407 long-term care outbreaks in 2009 and 2010 found that the outbreaks were associated with higher mortality and hospitalization at the nursing homes.2

Surveillance in the United Kingdom revealed a great burden of transmission in hospitals, as well. From 1992 to 2000, 40% of norovirus outbreaks occurred in hospitals while 39% were in long-term care facilities. Person-to-person transmission was much more common than foodborne spread.3

Health care workers were as likely to become infected as patients, but elderly patients or residents suffered the greatest severity of illness.

“Deaths were only reported from outbreaks in healthcare institutions. The populations in these institutions differ from those found in other settings by virtue of their greater age or presence of other underlying diseases,” the authors noted. “While norovirus infection is not likely the principal cause of death in most cases, this infection might constitute an additional burden on patients already weakened by other conditions and thus become an important contributory factor.”

European hospitals may have higher norovirus attack rates because of differences in their design, says Hall. For example, private rooms are more common in U.S. hospitals. But there also has been better surveillance of norovirus in Europe, he says. “It may well be a problem in hospitals that is underappreciated in the U.S.,” he says.


  1. Centers for Disease Control and Prevention. Outbreaks of Acute Gastroenteritis Transmitted by Person-to-Person Contact — United States, 2009–2010. MMWR 2012;61(SS09):1-12.
  2. Trivedi TK, DeSalvo T, Lee L, et al. Hospitalizations and Mortality Associated With Norovirus Outbreaks in Nursing Homes, 2009-2010. JAMA. 2012;308(16):1668-1675.
  3. Lopman BA, Goutam GK, Reacher M, et al. Two epidemiologic patterns of norovirus outbreaks: Surveillance in England and Wales, 1992-2000. Emerg Infect Dis 2003; 9:1-7.

Infection control for norovirus outbreaks

Controlling an outbreak of norovirus requires vigilant cleaning, hand hygiene, contact precautions and cohorting of patients, the Centers for Disease Control and Prevention recommends. CDC recomendations for norovirus include:

  • Using soap and water for hand hygiene after providing care or having contact with patients suspected or confirmed with norovirus gastroenteritis.
  • Wearing gowns and gloves when entering a patient care area.
  • Increasing the frequency of cleaning and disinfection of patient care areas to twice daily and frequently touched surfaces to three times daily, using products approved by the EPA for healthcare settings.
  • Cleaning and disinfecting surfaces starting from the areas with a lower likelihood of norovirus contamination (such as tray tables, counter tops) to areas with highly contaminated surfaces (such as toilets and bathroom fixtures). Change mop heads when new solutions are prepared or after cleaning large spills of emesis or fecal material.
  • Excluding ill personnel from work for a minimum of 48 hours after the resolution of symptoms. Once personnel return to work, the importance of performing frequent hand hygiene should be reinforced.
  • Establishing protocols for staff cohorting in the event of an outbreak of norovirus. Ensure staff care for one patient cohort on their ward and do not move between patient cohorts. (Patient cohorts may include symptomatic, asymptomatic exposed, or asymptomatic unexposed patient groups).
  • Excluding non-essential staff, students, and volunteers from working in areas experiencing outbreaks of norovirus.

[Editor’s note: For additional CDC recommendations and tools to fight norovirus go to:]