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Delaware Health Alert Network #294

January 25, 2013 1:47 pm

Health Alert

The Delaware Division of Public Health (DPH) is issuing this health alert to provide healthcare providers with updated information regarding an increase in clusters of norovirus cases and information regarding a new strain of norovirus (GII.4 Sydney) currently circulating in the United States (US) and now detected in Delaware.


Since January 1, 2013, DPH has investigated 13 reports of gastroenteritis clusters from healthcare facilities in Delaware, of which 8 (62%) were laboratory confirmed as norovirus. During the same period last year (January 2012), DPH investigated 6 reports of gastroenteritis clusters from healthcare facilities in Delaware (less than half the number under current investigation), of which 4 (67%) were laboratory confirmed as norovirus. The Delaware Public Health Laboratory (DPHL) is currently sub-typing norovirus strains. To date, DPHL has sub-typed specimens from one outbreak, which has been confirmed as the GII.4 Sidney strain. DPH is recommending that health professionals remain vigilant to detect potential increases in norovirus infection this season due to spread of the new norovirus variant, GII.4 Sydney.


The Centers for Disease Control (CDC) released a health alert about a new strain of norovirus, GII.4 Sydney, that is circulating in the US. CDC researchers analyzed 2012 data collected through the surveillance network CaliciNet on norovirus strains associated with outbreaks in the US. They found that 53% (141/266) of norovirus outbreaks reported during the last four months of 2012, were caused by the GII.4 Sydney strain. The new strain was first detected in Australia in March 2012, and has spread rapidly across the US. According to the CDC, healthcare facilities, including nursing homes and hospitals, are the most commonly reported settings for norovirus outbreaks because of the increased person-to-person contact. Approximately 59% of norovirus outbreaks in the US have occurred in long-term care facilities; 4% in hospitals.

Noroviruses are a group of viruses that cause gastroenteritis marked by an acute onset of severe vomiting, watery diarrhea, and nausea, which occurs 12 to 48 hours after exposure to the virus and lasts 24 to 72 hours after onset of symptoms. Noroviruses spread very rapidly and are highly contagious. Norovirus illness often occurs during the winter months. Shedding of the virus (peak: 2-5 days after onset) occurs primarily in stool but also in vomitus and is transmitted by contaminated food/water, person-to-person, fomites, and aerosols (from vomiting).

Infection Control Recommendations

Outbreaks in acute or long-term care settings can be prolonged; sometimes lasting months. Strict control measures including contact isolation (gowns and gloves when caring for symptomatic patients), discouraging visitation, exclusion of affected staff, and restricting new admissions into affected units) can be disruptive but are often required to curtail outbreaks.Close attention should be paid to good hand washing practices (preferably with soap and water). Masks and eye protection (in addition to gowns and gloves) should be used when handling patient’s vomitus or feces as norovirus can (at least theoretically) be transmitted by aerosol from vomitus.

Specific infection control recommendations for acute care and long-term care facilities are available at:


Notify DPH, Bureau of Epidemiology (24/7), of any gastroenteritis clusters at 1-888-295-5156. DPH will coordinate stool specimen testing for norovirus and other enteric pathogens with the Delaware Public Health Laboratory (

Additional Information


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