Guidelines for the public health management of gastroenteritis outbreaks due to norovirus or suspected viral agents in Australia
8.1 Standard precautionsFollowing standard infection control precautions can minimise the risk of norovirus outbreaks caused by person-to-person transmission in any institution or group setting or by an infected food handler. This requires a basic level of hygiene measures that can be implemented in any setting, regardless of whether a person is infectious or not.
Standard precautions are work practices required to achieve a basic level of infection control. They include:
- hand hygiene and cough etiquette
- the use of personal protective equipment (PPE)
- the safe use and disposal of sharps
- routine environmental cleaning
- incorporation of safe practices for handling blood, body fluids and secretions as well as excretions .
In order to reduce the risk of food handling related to norovirus infection and consequent outbreaks, it is essential to maintain food hygiene standards. These include:
- attention to hand hygiene
- prevention of gross contamination during food preparation
- provision of adequate handwashing facilities for food handlers
- ensuring that food handlers do not work while they have symptoms of gastroenteritis.
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Person-to-person outbreaks in semi-closed environments are usually difficult to control because the infectious dose of norovirus
is small, infected people excrete large numbers of viable virus particles and widespread environmental contamination occurs [38, 92].
Norovirus outbreaks in institutional settings may generate public concern and media interest and may cause severe illness and even result in deaths where cases have severe underlying illnesses. There is limited published evidence to guide best practice in management of outbreaks in specific settings, other than ACFs, cruise ships and hospitals.
The public health action for different settings may vary but regardless of the type of outbreak setting, three important control measures should be applied in the management of all outbreaks:
- cleaning and disinfection
- regular handwashing
- exclusion and cohorting of ill people.
8.2 Key measures for controlling outbreaksThe most important generic measures to be implemented in an outbreak setting are described below. These are recommendations only and may need to be varied according to the circumstances and type of setting for each outbreak. Some settings, such as hospitals, are likely to have access to PPE, whereas other settings may not. Nevertheless, the basic principles which support these recommendations can be applied to the management of institutional and community based outbreaks.
8.2.1 Hand hygieneTransmission of norovirus is usually person-to-person by the faecal-oral route and by contact with contaminated environmental surfaces . Cross-contamination by hands can assist in further propagating norovirus in outbreak settings. Studies have shown that fingers contaminated with norovirus could sequentially transfer virus to up to seven clean surfaces as well as from contaminated cleaning cloths to clean hands and surfaces .
Hand hygiene is an effective means of preventing further cases of gastroenteritis . Intervention studies have shown that effective handwashing can reduce absenteeism due to gastroenteritis and environmental contamination with norovirus . Hands must be washed with soap and water wherever possible, or decontaminated using an alcohol-based hand rub or gel before and after contact with any person in an outbreak setting and after activities that may result in personal exposure to viruses.
Hand hygiene should be routinely carried out in healthcare facilities in accordance with Hand Hygiene Australia’s Five moments
for hand hygiene (Hand Hygiene Australia: www.hha.org.au):
- before touching a patient
- before a procedure
- after a procedure or body fluid exposure risk
- after touching a patient
- after touching a patient’s surroundings.
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Washing and dryingHands should be washed systematically by rubbing all surfaces of lathered hands vigorously with a mild liquid handwash for 10-15 seconds under running water. A review by the World Health Organization (WHO) on hand hygiene found that water temperature does not appear to be a critical issue for handwashing. Although their review was based on limited evidence, it seems that time and friction when washing hands are more important aspects than temperature .
When washing is complete, thoroughly rinse hands under running water and then pat dry using a disposable paper towel, a single clean cloth towel or a fresh portion of a roller towel to prevent recontamination. If elbow or foot controls are not available a paper towel or the used towel should be used to turn taps off to prevent the risk of cross infection.
Alcohol-based preparationsSoap and water should be used wherever possible when washing hands during outbreaks. Skin disinfectants formulated for use without water (e.g. 70–80% alcohol-based solutions) can be used to decontaminate hands when handwashing facilities are not available. However, they do not replace the importance of handwashing with soap and water during outbreaks. Alcohol preparations are not useful if hands are visibly contaminated with body fluids, faeces or vomit. Hands should then be washed as soon as appropriate facilities are available.
Because norovirus cannot be cultured, the efficacy of alcohol-based preparations against this virus is difficult to determine. Studies have shown that alcohol-based hand rubs containing 60% alcohol can reduce the infectivity titres of three non-enveloped viruses (rotavirus, adenovirus and rhinovirus) by 3 to 4 logs. Other non-enveloped viruses, such as hepatitis A and enteroviruses require 70–80% alcohol to be reliably inactivated. The inactivation of non-enveloped viruses is influenced by temperature, the ratio of disinfectant to virus volume and protein load.
When various 70% alcohol solutions were tested against a surrogate of norovirus, ethanol with 30 minute exposure had demonstrably superior virucidal activity compared to the others. Solutions containing alcohol may be expressed as a percentage by weight, which is not affected by temperature or as a percentage by volume, which may be affected by temperature and other variables. Alcohol concentrations in antiseptic hand rubs are usually expressed as a percentage by volume. Alcohol solutions containing 60–80% alcohol are effective, with some studies reporting contradictory findings with higher concentrations being less potent . Handwashing formulations that combine compounds such as ethanol with quaternary ammonium compounds and organic acids, may be more efficacious against these non-enveloped viruses .
Alcohol-based hand rubs should not be removed from clinical settings or patient care areas during an outbreak, rather hand washing should be promoted above the use of alcohol-based hand rubs during an outbreak.
8.2.2 Personal protective equipmentIn outbreak settings, appropriate personal protective equipment (PPE) should be used if possible in each setting of potential norovirus transmission to minimise infection risk. Splashing of faeces or aerosols from vomiting has the potential of suspending norovirus in the air and falling onto food or surfaces. Hand hygiene should be carried out at all times, particularly after removing PPE to minimise spread of viruses .
GlovesDisposable gloves should be worn if having direct contact with ill persons and when it is likely that hands will be contaminated with faeces or vomit. Hands must be washed before and after using disposable gloves, which should be single use only . If gloves are not available, it is essential that hands be washed immediately after any contact with ill and well people during an outbreak.
MasksNoroviruses are highly infectious and a small number of particles in aerosolised vomit can cause infection. A mask (surgical type, fluid repellent paper filter mask) should be worn when there is potential for aerosol dissemination. This may occur when attending a vomiting person or cleaning areas or surfaces that are visibly contaminated by vomit or faeces. Surgical face masks provide sufficient protection against droplet transmission of noroviruses. During outbreaks, staff attending vomiting patients or cleaning areas contaminated by vomit or faeces should use surgical masks or other respiratory protection to prevent infection, as this can significantly reduce subsequent illness in staff .
GownsProtective, impermeable gowns or plastic aprons should be worn if potential exists for splashing, splattering or spraying of vomit or faeces. Impermeable gowns and plastic aprons will protect clothing and skin from contamination with faeces and vomit. Ideally, aprons will be single use that can be disposed of, although reusable plastic ones can be washed with detergent and water between uses. If the items have been visibly contaminated with faeces or vomit a bleach solution should be used to decontaminate (see section 8.2.3). Protective clothing contaminated with faeces or vomit should be removed as soon as possible and disposed of without generating aerosols (see section 8.2.5).
EyewearProtective eyewear such as face-shields or goggles should also be worn where the potential exists for splashing, splattering or spraying of vomit and faeces. Reusable goggles should be washed with detergent and water between uses. Visible contamination with faeces or vomit should first be washed off with soap and water, followed by cleaning with bleach solution (see section 8.2.4).
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8.2.3 Environmental cleaningProlonged outbreaks in semi-closed settings suggest that norovirus survives well in the environment and can spread via environmental surfaces. A continuation of outbreaks on consecutive cruise ship trips has demonstrated environmental persistence and led to recommending the need for extensive disinfection measures . In another study on repeated outbreaks in cruise ships, illness was associated with sharing bathrooms and having a cabin mate who vomited. Contaminated shared bathrooms and environmental contamination were implicated in the transmission of infection. Subsequent outbreaks were prevented by frequent and thorough bathroom cleaning and rapid cleaning of contaminated rooms . These reports confirm the need for a comprehensive and responsive cleaning and disinfection program during as well as at the end of an outbreak. This section details information on cleaning and disinfection during outbreaks of viral gastroenteritis, with further information contained in Appendix 4.
Chemical agentsThere is no direct evidence to support the use of particular chemical agents for environmental disinfection as there is no viral culture system available for norovirus. Previous studies have used the feline calicivirus (FCV) as a surrogate for norovirus because of their relatedness. It is known that FCV is inactivated by heat at 60°C and by sodium hypochlorite (bleach) at 1000 parts per million (ppm) (0.1%) but not by ethanol. A study found that FCV was completely inactivated when exposed to 1000 ppm freshly reconstituted granular hypochlorite (dichloroisocyanurate) or 5000 ppm hypochlorite solution. Quaternary ammonium product, detergent and ethanol did not completely inactivate the virus . Quaternary ammonium compounds perform as low level disinfectants and are ineffective against norovirus because they act by disrupting viral envelopes, and norovirus are nonenveloped virus particles.
There has been debate on how well data on inactivation of FCV reflects efficacy against norovirus because of the different physiochemical properties between the two viruses. Nevertheless, as there is little data to support the efficacy of chemical agents and based on what is known about FCV, most local and international guidelines on norovirus recommend the use of hypochlorite at 1000 ppm. Household bleach comes in a variety of strengths ranging from 2–5% sodium hypochlorite solution as indicated on the product label.
Details for diluting bleach to obtain a 1000 ppm solution are in Appendix 4. In order for bleach to be effective at a concentration of 1000 ppm (0.1%) it needs:
- sufficient time to kill the virus – at least 10 minutes contact time
- environmental surfaces to be free of vomit or faeces or any other organic matter
- dilution of bleach to made up fresh, just before using.
Cleaning equipment and agentsBleach should be applied to hard, non-porous, environmental surfaces at a concentration of 1000 ppm. However, cleaning with bleach should be preceded where possible with a neutral detergent clean, the detergent providing a surfactant to release oils and bio-burden to enable penetration of the chemical. Detergents used for environmental cleaning should remove soil or dirt, suspending this in water, to be followed by rinsing the area free with little or no residue. Neutral pH detergents are best for environmental cleaning because they are less likely than acid or alkali detergents to damage metals such as stainless steel or to cause skin irritation .
Where possible, cleaning equipment such as cloths should be disposable and discarded immediately after use in each patient area in a leak proof plastic bag. Heat disinfection (pasteurisation to 60°C) has been used successfully under laboratory conditions and may be useful for items that cannot withstand bleach. It is important in the process of terminal cleaning of an area for the cleaner to use PPE (gown, gloves and a surgical mask) to prevent the cleaner becoming infected with norovirus. Transfer of infection to the cleaner has been implicated when carpets have been steam cleaned. Public health agencies should advise agencies cleaning an affected facility to use appropriate PPE for cleaning.
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Environmental surfacesTo assist in preventing transmission in an outbreak setting, frequently touched environmental surfaces such as door handles, bathroom taps, lift buttons, washrooms, phones and tables should be cleaned more frequently than the routinely recommended daily cleaning. Particular attention should be paid to toilet seats, flush handles, wash-hand basin taps and toilet door handles. These should be cleaned at least twice a day as well as after any high usage times. Surfaces should be cleaned using detergent and warm water. A bleach solution diluted to 1000 ppm may be used to disinfect surfaces that are visibly soiled. The manufacturer’s recommendations for use and occupational health and safety instructions should be followed when using bleach.
Terminal cleaning of an affected area, unit or section should be carried out 72 hours after resolution of symptoms in the last case. This takes into account the period of maximal infectivity of 48 hours plus the average incubation period of 24 hours for any newly infected individuals . However, it may be unrealistic to wait for return of formed stools in all cases. At minimum, terminal cleaning should not be carried out until at least 72 hours after onset in the last case and 72 hours since uncontrolled vomiting or diarrhoea with contamination of the surrounding environment. Terminal cleaning should involve cleaning of all surfaces, furniture, bedding, equipment and items in contact with ill persons with detergent and water, followed by wiping with a bleach solution. Alternatively a combined detergent/sodium hypochlorite solution can be used as a one-step terminal clean. Terminal cleaning should be carried out before an outbreak is declared ‘over’ (see section 7.5).
8.2.4 Cleaning up vomit or faecesVomit can produce aerosols suspended in the air and fall onto food or surfaces. If a person vomits in a public area, all people should be removed from the vicinity and the area cleaned immediately. Persons cleaning vomit or faeces should wear gloves, apron and a mask. Paper towels should be used to soak up excess vomit and faeces and disposed of in a leak proof plastic bag. The area should be cleaned with detergent and warm water using a disposable cloth, and discarded into a leak proof plastic bag. The area should be disinfected with bleach solution, if not subjected to damage by bleach.
Splash incidentsIf there has been exposure to faeces or vomitus on body parts other than the hands, the area should be washed with soap and water if on the skin, with water if the eyes are splashed and if in the mouth, the body fluid should be spat out and the mouth rinsed several times with water .
CarpetsCarpets that have been soiled by faeces or vomit are difficult to disinfect. Bleach is not generally recommended as prolonged contact is required and carpet is usually not bleach resistant. Soiled carpets should be cleaned with detergent and warm water and then steam cleaned. Vacuum cleaning carpets has the potential to recirculate norovirus and is not recommended. However, if necessary, the use of separate ducted systems or HEPA-filtered devices may be considered for each area. The cleaner should use PPE (gown, mask and gloves) to prevent norovirus infection. Repeated outbreaks of norovirus have occurred even when carpets have been steam cleaned.
Soft furnishingsSoft furnishings that may be damaged by bleach should be cleaned with detergent and warm water and if possible steam cleaned. If mattresses have been contaminated they should also be steam cleaned. Contaminated pillows should be laundered in the same way as linen (see section 8.2.5). However, if they are covered with an impermeable cover, pillows should be cleaned with detergent and warm water followed by wiping with a bleach solution.
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8.2.5 LaundryGloves should be worn when handling soiled linen. PPE may be required if there is potential for contamination by way of splashing, spraying or splattering of faeces or vomit. Soiled linen or clothing should be removed immediately and placed in a collection bag or leak proof plastic bag. There should be minimal handling of soiled linen or clothing to prevent generating further aerosols. Contaminated linen, blankets or clothing should be washed as usual in detergent for the maximum washing cycle. Used non-disposable mop heads should be laundered in a hot wash. Exposed personal effects (e.g. wall hangings etc.) should preferably be hot-washed through the laundry and bleach cleaned where possible.
Where an outbreak becomes protracted or is difficult to contain, consideration should be given to outsourcing laundry services to allow high quality cleaning of the laundry. If an external laundry service is used by the institution they should be informed about the outbreak so they can take necessary precautions to avoid infection.
In an aged care or health care setting, linen should be placed in a leak proof bag or alginate bag at the point of generation. Soiled linen should not be left on the floor or in corridors. The practice of hosing off gross soiling from clothing and linen prior to laundering is not recommended.
8.2.6 FoodOnly catering or kitchen staff should have access to the kitchen at any time; this is particularly important during an outbreak. Ill people should not take part in food handling duties and should not return to their usual food handling duties until 48 hours after their symptoms have ceased. All appliances, work benches and equipment need to be effectively sanitised (refer to manufacturer’s instruction). Communal dining areas should be closed during an outbreak. If this cannot be carried out, the areas need to be sanitised after each use. All utensils, cutlery, crockery and glassware are to be washed in the usual manner with detergent and hot water. Dispose of any exposed food, that is, food that has been handled by an infected person or food that may have been exposed to someone vomiting in close proximity.
8.2.7 ExclusionIll people should be sent home immediately and excluded from child care, preschool, school or work for 48 hours after all symptoms have stopped. Maximum viral shedding probably occurs 24–48 hours after exposure; therefore it is a reasonable and accepted recommendation that workers be excluded for 48 hours after symptoms have stopped. As viral excretion can persist for days it is not practical or of benefit to require clearance of norovirus from stools before a person returns to work.
There is very limited data about the how infectious the virus is during post-symptomatic shedding because of the lack of laboratory assays to measure norovirus infectivity . However, the load shed in the post-symptomatic phase is lower than the load shed in acute illness, and the evidence for spread in these individuals is not as good as the evidence for spread during symptomatic illness . Better information on the duration of viable viral shedding and of the incidence of asymptomatic shedding of viable virus would enable more evidence-based recommendations for exclusion of workers.
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8.2.8 Isolation and cohortingAn attempt should be made to separate ill people from well people (‘cohorting’), especially if the outbreak setting is in a semiclosed environment and people are required to live in a household-like situation sharing the same facilities. However, there should be limited moving around of norovirus-infected people. In such settings, common areas should be closed off in an outbreak situation. If this is not possible, unwell people should not use common areas. If unwell people must share a room with others, strict handwashing and PPE procedures should be in place for anyone entering that room. If possible, separate toilet facilities should be allocated for affected people. If possible, ill people should be restricted to their room and for 48 hours after resolution of symptoms. This measure is intended to prevent susceptible individuals from becoming infected as norovirus immunity is known to be strain specific and short-lived.
If the outbreak is confined to one area, people in that area should avoid contact with people in unaffected areas. There should be dedicated people to look after ill persons and they should not be involved in food preparation. If dedicated people are not available, they should observe strict handwashing and use of PPE procedures when moving between ill and well people or affected and unaffected areas.
8.2.9 Visitor restriction and signageIn an attempt to limit the further spread of infection, visiting affected areas should be restricted during the period of an outbreak. Whether restrictions to visiting pertain only to the affected area, or to the whole facility, depends on whether affected and unaffected areas are separate enough to prevent further spread of infection. If limited visiting is permitted, visitors entering a facility where there is an outbreak should be made aware of the risk of transmission and infection; this may be done by placing signs at all entrances to the facility (see Appendix 5). Restriction of non-essential services to the institution should be recommended. Visitors should wash their hands on arrival and when leaving the facility. Visitors experiencing any symptoms of gastroenteritis should be advised not to visit the institution until 48 hours after cessation of symptoms. Consideration should be given to restricting visitors from bringing food into the facility.
8.2.10 ClosureIn some outbreaks that are difficult to control and where there is significant ongoing risk of infection by periodic renewal of the susceptible population, such as cruise ships and camps, it may be necessary to close the facility until it can be cleaned and disinfected properly. However, this decision will have to be made on a local level in conjunction with the facility, the public health agency, local government and environmental health.
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8.3 TrainingIt would be beneficial for all institutions, community settings and food establishments at risk of norovirus outbreaks to provide a specific program of education and training for staff about management of such outbreaks. This could be incorporated in induction training programs and also be carried out at times of an outbreak occurring. Workplace education could include the following:
- cleaning and disinfection procedures
- isolation of affected persons
- transfer of ill persons
- exclusion of ill people
- importance of correct hand hygiene covering all hand surfaces for adequate duration, using the appropriate product and carried out at appropriate times
- personal hygiene, proper glove use and correct food handling practices for food handlers
- transmission of viral gastroenteritis and infection control procedures.
During an outbreak, regular promotion of hand washing is recommended. In order for people to wash their hands during an outbreak they must have access to water, handwash (preferably liquid, not cakes of soap) or alcohol-based hand rubs or gels and disposable paper towels or single cloth towel. Where possible, institutions need to have access to PPE and staff need to be trained in how and when to use them. Training on cleaning procedures is important. If a vomiting incident occurs in any public area, including restaurants, staff members need to know how to clean and disinfect the area correctly to prevent further transmission through environmental contamination and aerosolisation of vomit. Employers should ensure that employees are properly trained in food safety as it relates to their assigned duties.
Management should support the recommendation that staff should not return to work for 48 hours after diarrhoea or vomiting stops. Staff should not feel compelled to return to work earlier for fear of losing their employment or due to staff shortages. This is particularly important where staff have a role in handling or preparing food. Many foodborne outbreaks of norovirus are the result of people working while they have symptoms of gastroenteritis.