Increase in Norovirus Activity in New Hampshire

|January 07, 2014

Since December 1, 2013, the New Hampshire Division of Public Health Services (NH DPHS) has received 16 reports of gastroenteritis outbreaks in institutional settings, with eight outbreaks being reported in the last week alone. Most of these outbreaks have a confirmed cause of norovirus, a common viral infection in the United States.

Noroviruses are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans and are named after the original strain "Norwalk virus," which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. Currently, there are at least five norovirus genogroups, three of which can infect humans (GI, GII, GIV). Norwalk virus is in group GI. Noroviruses identified in New Hampshire over the last several years are predominantly genogroup II (GII).

Noroviruses are highly communicable and can be transmitted in a number of ways, including person-to-person contact, consumption of contaminated food and water, airborne droplets of vomit, and contact with contaminated surfaces. Symptoms normally last 12-60 hours and commonly include vomiting and diarrhea. Primary symptoms may be accompanied by abdominal cramps, nausea, fever, or headache. Available treatment is supportive therapy for dehydration, and fortunately symptoms usually resolve within 48 hours.

The NH DPHS recommends:

1. Increased awareness and vigilance for outbreaks of gastroenteritis in healthcare facilities, schools, and childcare settings, which may be caused by norovirus.

2. Strict adherence to infection control practices during a suspected outbreak.

3. Awareness of resources for institutional settings experiencing a gastrointestinal outbreak.

4. Timely reporting of all suspected outbreaks to the NH Department of Health and Human Services Bureau of Infectious Disease Control at 1-603-271-4496 (after hours, 1-800-852-3345 ext. 5300).

Infection Control Recommendations during an Outbreak for All Institutional Settings

1. Practice frequent hand washing by all staff, patients, residents, or students. Proper hand washing with soap and running water for at least 20 seconds is the most effective way to reduce norovirus contamination on the hands. Hand washing is particularly important after contact with infected individuals, on leaving affected areas, and before handling food or drinks.

2. Use gloves and aprons whenever contact with an infected individual or contaminated environment is anticipated. A surgical or procedure mask and eye protection or a full face shield should be used if there is an anticipated risk of splashes to the face during the care of ill persons, particularly among those who are vomiting.

3. Increase the frequency of cleaning and disinfection of frequently-touched surfaces such as water taps, door handles, and toilet or bath rails.

4. Promptly clean areas contaminated with vomit and feces and then disinfect using freshly prepared sodium hypochlorite with a concentration of 1,000-5,000 ppm (5-25 tablespoons household bleach [5.25%] per gallon of water). Whenever possible, this chlorine bleach solution should be used; however, a commercial product registered with EPA as effective against norovirus may be used alternatively. A list of EPA-approved products is available at

5. Clean soiled carpets and soft furnishings with hot water and detergent or steam clean; avoid vacuum cleaning.

6. Review kitchen practices and ensure that gloves are worn by all food service workers when handling ready-to-eat foods. Assess health status of food service workers and exclude symptomatic individuals from work until 48 hours after resolution of symptoms.

7. In schools and childcare facilities, assess health status of students and staff and exclude all symptomatic individuals from school or work until full recovery.

8. In healthcare facilities, assess health status of all healthcare workers and exclude symptomatic individuals from direct patient care until 48 hours after the resolution of symptoms.

Additional Recommendations for Healthcare Facilities

9. Restrict or defer admissions to affected units and wards.

10. Stop all group activities temporarily.

11. Exclude non-essential staff from affected areas and interrupt the movement of interdepartmental staff.

12. Notify visitors and provide instructions regarding hand washing.

13. Conduct terminal cleaning 72 hours after resolution of the last case.

These recommendations are discussed in greater detail in the Centers for Disease Control and Prevention's Norovirus Outbreak Management and Disease Prevention Guidelines, available at:

The Healthcare Infection Control Practices Advisory Committee's guideline for the prevention and control of norovirus outbreaks in healthcare settings is available at:

Additionally, a toolkit for healthcare facilities experiencing a norovirus outbreak is available at:

Laboratory Testing for Norovirus

Stool testing for norovirus is available at some commercial laboratories and the New Hampshire Public Health Laboratories (NH PHL). Available tests use real-time reverse transcriptase polymerase chain reaction (Real Time RT-PCR) methods to detect the virus in stool specimens.

While virus can sometimes be found in stool samples taken as late as two weeks after recovery, identification of the virus is best made from stool taken within 48 to 72 hours after onset of symptoms with good results obtained on samples taken as long as five days after onset. The NH DHHS recommends norovirus testing for suspected outbreaks of norovirus and requests that stool specimens get sent to the NH PHL after consultation with the NH DHHS Bureau of Infectious Disease Control (see reporting information below). Specimen testing at the NH PHL for non-outbreak specimens is also available at a cost.

Whole stool specimens should be collected in a sterile container, labeled with patient identifiers, and placed in a plastic bag. Samples must be frozen, refrigerated or placed on ice, have a completed PHL requisition form, and be delivered to the NH PHL as soon as possible for best testing results.

Reporting of Suspected Outbreaks

Individual cases of norovirus are not reportable in New Hampshire unless suspected to be part of an outbreak. To report suspected outbreaks, call the Bureau of Infectious Disease Control at 1-603-271-4496 (toll free at 800-852-3345, ext. 4496). After hours, call 1-800-852-3345, ext. 5300, and ask for the public health professional on call. The public health professional will discuss appropriate management of the suspected outbreak, including laboratory testing. To discuss specific questions about laboratory testing and specimen submission you may also contact the NH PHL at 1-603-271-4620.

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