Norovirus
Introduction
Noroviruses are non-enveloped viruses. They frequently cause infectious gastroenteritis and have been associated with outbreaks in hospitals, nursing and residential homes, schools, cruise ships, camps, and restaurants. It affects people of all ages.
Clinical symptoms
The average incubation period is 12 to 48 hours. Onset symptoms can be gradual or abrupt, including nausea, sudden onset of (often projectile) vomiting, abdominal cramps, and diarrhoea. In addition, it may be accompanied by low-grade temperatures. The disease is self-limiting, and most patients recover within 1-3 days. In rare cases in those with severe infections who cannot maintain hydration, IV fluid replacement may require hospitalization to prevent dehydration. No vaccine or antiviral agent is available.
After infection, immunity to norovirus is short-lived, and reinfection can occur if exposed to different strains due to a lack of cross-strain immunity. Therefore, it is possible to have multiple norovirus infections in a short period (~ 4-6 months)..
Diagnosis
- PCR can be used to detect noroviruses because other methods are not sensitive enough to guarantee the absence of norovirus.
- Faeces should sent to the Laboratory for confirmation, as other specimens are not sensitive enough to ensure the absence of norovirus.
- Once confirmed, there is no need to retest unless the patient is at high risk of chronic infection.
Mode of Transmission
- Humans are the only known carriers of norovirus. The virus is highly infectious and requires only 10 to 100 virions to cause infection.
- The primary mode of viral transmission is faecal-oral spread through exposure to contaminated food or water. Secondary infection results from person-to-person contact, aerosolized vomitus, contaminated hands, items and equipment, environment and infected food handlers.
- After infection, prolonged asymptomatic shedding may continue for up to three weeks in immunosuppressed individuals. These patients may continue to contaminate the environment even when an outbreak ends.
Infection Control Measures
- Triage: Avoid admitting anyone known or suspected to be infected with norovirus. If possible, test all symptomatic patients at admission or when they develop symptoms.
- Patient placement: If viral gastroenteritis is suspected, move the patient to an en suite single room as soon as possible and implement contact IPC precautions. If a single room with an en suite toilet is not available, they must be provided with a commode or bedpan. Send a stool specimen to the microbiology laboratory. Notify the infection control team (ICT).
Patients who have not yet developed symptoms but have been exposed to symptomatic patients should be kept under close observation. If diarrhoea develops, then s/he must be isolated in an en suite single room. In an outbreak situation, patients can be placed in a designated (cohort) area with contact IPC precautions for all patients.
- Transfer of patients: Avoid patient movement to unaffected wards/units and health care facilities (HCFs) unless medically urgent. If the patient is clinically well, they can be discharged to their own home. Transfer of patients from an outbreak ward to other HCFs, including nursing and residential homes, should be postponed until the patients are asymptomatic for at least 48–72 hours and exposed patients in the same bay have not developed symptoms for at least 48 hours to ensure that they are beyond incubation period.
- If a patient’s transfer is necessary, the receiving facility must be informed so that the patient can be isolated in an en suite single room.
- As a part of control measures, suspending new patients’ admission may become necessary until the outbreak is over.
- Visitors:Visiting should be restricted, and any visitors who have any signs or symptoms of gastroenteritis are requested not to visit the ward.
Visitors do not need to wear protective clothing unless they provide direct care to a patient. However, they should be advised to wash their hands with soap and water before entering or leaving the room and not to visit other patients in the ward or hospital. - Staff:Norovirus frequently affects staff as well as patients. Staff should pay attention to hand hygiene. No food or drink should be consumed in clinical areas. If symptoms develop, staff should stop work immediately, inform their line manager, and submit specimens if requested. They should liaise with the Occupational Health Department and return to work on their advice. They usually should be symptom-free for 48 hours. Food handlers should not return to work until symptom-free for 72 hours.
- Hand hygiene: Wash hands with soap and water.
- Offer food and drink that is covered or individually wrapped and remove anything that becomes contaminated,g. fruits and other edible items. Water jugs and glasses used for patients must be covered.
- Personal protective equipment: Wear single-use, non-sterile gloves and a plastic apron for contact with secretions and excretions (e.g. handling bedpans, vomit bowls, and urinals), handling the patient’s clothes and bedding, and contact with the patient or their immediate environment. Wear masks when clearing vomiting and diarrhoea.
Always wash hands after removing gloves and plastic aprons.
- Decontamination of items/equipment: Avoid soft furnishings and non-wipeable items. Clean and decontaminate all reusable items and equipment. Reusable bedpans must be disinfected in a bedpan washer or use a macerator for single-use disposablebedpans and urinals. Ensure the bedpan washer and macerator work correctly and the sluice is clean, dry and tidy. Non-disposable bedpans should be stored inverted.
- Environmental cleaning: Decluttering wards is essential to reduce the bioburden to allow effective cleaning and disinfection of environmental surfaces. All unnecessary items from locker tops and tables must be removed. The frequency of routine cleaning and disinfection of the ward/unit should be reviewed and increased with particular emphasis on toilets, sluices, and hand-touch surfaces. There is no need to sample the environment routinely.
After thoroughly cleaning with a neutral detergent, disinfect the area with a freshly prepared hypochlorite solution of 1,000 ppm. This includes the environment around symptomatic patients, toilets, commodes, bedpans, bathrooms, showers, and the sluice (especially the macerator and bedpan washer). During cleaning, special attention must be paid to frequently hand-touched surfaces, e.g. flush handles, wash hand basin taps, and toilet door handles. Wear a mask when clearing faeces and vomit, and disinfect the area as per local protocol.
- Laundry: All laundry must be segregated at the point of generation and processed as ‘infected’ linen as per local policy. In the home setting, soiled clothing or bedding should be washed separately from other clothes in a domestic washing machine using detergent and a high-temperature (at 60°C, if possible) wash cycle. Wear disposable gloves to handle contaminated items.
Reporting and Outbreak Management
- If an outbreak of norovirus is suspected, send specimens to the Laboratory for testing. Seek advice from the IPC team in the hospital. The first contact for advice in a community or Care Home setting may be the Home/unit manager, the GP and the Public Health Agency (PHA). All precautions should be implemented immediately (including out-of-hours). Inform local facilities that you are experiencing an outbreak. Risk-assess whether unit/facility closures or staff/visitor restrictions are needed and feasible.
- To expedite the investigation, it is necessary to create a list of affected patients with the date of onset of diarrhea or vomiting. If admitted to the hospital, note the date and reason for admission. If an outbreak is suspected, follow the guidance in the policy for Outbreak Management. Closing a ward/ unit to new admissions may be necessary. This decision is made in consultation with the IPC team in acute settings or the PHA in community settings. During an outbreak, staff movement may need to be restricted, and staff from affected areas should not work in unaffected areas.
- If possible, maintain control measures for 72 hours after the last symptoms in the last case disappear to prevent recurrence. Before re-opening, the ward to new admissions, it must be thoroughly cleaned and disinfected, and all beds and curtains changed .
References
- HIS Guidelines for the management of norovirus outbreaks in acute and community health and social care settings. Journal of Hospital Infection 2023; 136:127-191.
https://www.journalofhospitalinfection.com/action/showPdf?pii=S0195-6701%2823%2900043-9
- Guideline for the Prevention and Control of Norovirus Gastroenteritis Outbreaks in Healthcare Settings. Atlanta: Centers for Disease Control and Prevention, 2011.
https://www.cdc.gov/infectioncontrol/pdf/guidelines/norovirus-guidelines.pdf
- European Centre for Disease Prevention and Control. Prevention of norovirus infection in schools and childcare facilities. Stockholm: ECDC, 2013.
- Guidance for the Management of Norovirus. Infection in Cruise Ships. London: Health Protection Agency, 2007.
- Guidelines for the Management of Norovirus Outbreaks in Acute and Community Health and Social Care Settings. London: UK Health Protection Agency, 2012.