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Norovirus: infection and infection prevention
through hygiene in the home
This leaflet has been put together to provide background information and advice on
what to do if there is risk of spread of norovirus in the home (household) setting. The
target audiences for this briefing material are healthcare professionals, the media
and others who are looking for background understanding of norovirus infection
and/or those who are responsible for providing guidance to the public on how to
prevent the spread of norovirus in their homes.
What are noroviruses (NVs)?
Noroviruses consist of several groups of viruses that have been named after the
places where the outbreaks occurred. They were previously referred to as Small
Round Structured Viruses (SRSV) or Norwalk-like viruses (NLV). Common names for
the illness caused by these viruses are: viral gastroenteritis, acute nonbacterial
gastroenteritis, food poisoning, and food infection. The illness is sometimes referred
to as ‘winter vomiting disease’ even though it now occurs all year round.
A mild and brief illness usually develops 12-48 h after infection and lasts for 24-60
hours. There are no treatments available, but the disease is self-limiting and mild.
The main symptom of infection is projectile vomiting, nausea, diarrhoea and
abdominal pain. Headache and mild fever may also occur. The virus is highly
contagious and can spread rapidly from person-to-person via hands and surfaces.
Good hygiene is vital to breaking the chain of infection transmission in the home to
other family members.
How does norovirus get into the home?
 An infected family member may act as the primary source of infection in the
home. Up to 30% of people infected show no symptoms and may spread the virus
unknowingly. People can continue to harbour and shed the virus for up to 3 or 4
weeks after symptoms have ceased, though the rate of shedding decreases
rapidly over the first few days. Peak viral shedding occurs 2--5 days after infection,
with a viral load of approximately 100 billion viral copies per gram of feces.
 Through infected food purchased from retail premises. The most common
sources are filter feeding shellfish (e.g. oysters, mussels and clams) which are
harvested from sewage-contaminated waters, or vegetables grown or washed in
polluted water. The virus cannot grow in food, but can survive, even in frozen food
for long periods.
How does norovirus spread in the home and cause infection?
Norovirus spreads via the common routes for stomach bugs. It enters the body to
infect the gastrointestinal tract (GI) via the mouth. It enters the mouth either on food
or by contaminated hands (fingers) touching the mouth. It can also sometimes enter
the GI tract through the inhalation of aerosolised vomit.
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Infected family members can spread infection in a number of ways.
Projectile vomiting represents the major route of cross infection. It is estimated
that 30 million particles may be distributed as an aerosol into the environment
during a vomiting attack. The aerosol can settle on surfaces in the home where
the virus can remain infective on hard surfaces and fabrics for several days. The
virus can multiply in the stomach and large quantities of virus are then shed in
faeces into the toilet. Where someone has fluid diarrhoea, flushing the toilet
produces an aerosol which can settle on surfaces such as the toilet seat or toilet
flush handle. The virus is highly contagious, a dose of as little as 6-10 particles
may be sufficient to cause infection. Spread of infection from an infected to an
unaffected family member can occur in a number of ways:
- from hand to mouth: the hands of an uninfected person can be
contaminated by shaking hands with an infected person, touching a surface
which has been contaminated by aerosol particles or touched by an infected
person with contaminated hands.
- via food: this can happen if an infected family member handles or prepares
ready-to-eat foods such as sandwiches, salads etc for other family members.
- via inhalation of infected vomit: there is some evidence to suggest that
infection can occur by inhalation of infected aerosol particles. This probably
occurs mainly if family members are in close proximity to the infected person
during, or immediately after, a vomiting attack.
- contaminated food: such as shellfish can cause infection when it is eaten
raw or has not been properly cooked. The virus can also spread to other
foods (cross contamination) with which the shellfish or other contaminated
food has been in contact.
Further information on the transmission of norovirus in the home can be found in a
2013 IFH report1
Care of infected persons
There is no treatment available for norovirus infections, but the symptoms usually
only last for 1-3 days. Family members should drink plenty of fluids to prevent
dehydration which can easily occur. The young and very old require special care in
this respect. As far as possible the infected person should keep away from other
family members during the “vomiting phase”, and should keep away from work or
school for at least 3 days after symptoms have subsided to avoid passing on the
infection to others.
Frequency of the Disease
Indications are that norovirus is now the most significant cause of infectious intestinal
illness in the developed world. Noroviruses are detected in ≈50% of outbreaks across
Europe and the United States. Expert opinion is that norovirus strains now circulating
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are more “virulent” and more easily spread from person-to-person via hands and
surfaces or during food-handling. Although norovirus has achieved notoriety because
of the outbreaks which have occurred in hospitals, hotels and cruise ships, norovirus
infection also commonly circulates in the home and community. Since norovirus
infections are largely self-limiting within a few days, sporadic infections are not
usually reported, which means that only limited data is available on the prevalence of
infections in the community and home. However 2 community-based studies give
some idea of the extent of the problem.
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In reality only a small proportion of the total cases (which includes outbreaks and
sporadic (individual) infections) of norovirus are reported to surveillance. An
estimate of the true infection rates comes from a UK study of the incidence of GI
in the UK in the community which indicates that there are up to 17 million
sporadic community cases of infectious intestinal disease annually. Of these,
norovirus accounts for 3 million cases and 130,000 GP consultations.2 The data
suggest that up to 1 in 4 people in the UK suffer from a GI illness every year. This
community-based study, estimated that, for every one reported case of norovirus,
another 288 cases occur in the community.
From a community study reported in the Netherlands in 1999 it was estimated
that relative to the population of the Netherlands (16 million), 650,000 norovirus
gastroenteritis cases occur annually.
Approximately 21 million illnesses caused by norovirus are estimated to occur
each year in the United States, approximately one quarter of which can be
attributed to foodborne transmission.3
A 2011 review in Morbidity and Mortality Weekly4 states that norovirus infections are
prevalent throughout the world, with initial exposure typically occurring early in life. A
review of 31 community, outpatient, and hospital-based studies in both developed
and developing countries estimates that noroviruses account for 10%--15% of severe
gastroenteritis cases in children aged <5 years and for 9%--15% of mild and
moderate diarrhea cases among persons of all ages. In population-based studies
from Australia, England, Hong Kong, and the Netherlands, norovirus infection has
accounted for 9%--24% of gastroenteritis cases. In these studies, infection was more
frequent in certain age groups (e.g., children aged <5 years and adults aged >65
years). Studies also demonstrate relatively high prevalence of norovirus-positive
samples in asymptomatic persons, ranging from 5% in the Netherlands to 16% in
England.
Most data on GI disease comes from outbreaks reported to national surveillance.
For European countries, the annual Community Summary Report by the European
Food Safety Authority (EFSA) and European Centre for Disease Prevention and
Control (ECDC), gives an overview of the latest trends and figures on the occurrence
of zoonoses and zoonotic agents in humans, animals and foodstuffs in the 27
European Union (EU) Member States and the European Free Trade Association
(EFTA) countries.5 Further information on the incidence and prevalence of norovirus
infection can be found European Centre for Disease Prevention and Control. Annual
Epidemiological Report 2013.6 These publications are updated annually. Data for the
US is generated through the National Outbreak Reporting System.7
National surveillance systems have established that norovirus strains periodically
emerge either globally or nationally, and displace other strains causing increased
disease incidence. Norovirus differs from other agents of gastroenteritis because
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immunity seems to be short-lived. Thus individuals may be protected for only a few
months following an infection before they become prone to infection once more.
Norovirus in relation to the home setting is also reviewed in a 2008 IFH report.8
Preventing the spread of norovirus infection in the home
In situations where there is risk of spread of infection in the home the following
hygiene measures should be rigorously implemented. It must be remembered that
norovirus can also be spread by people who have no symptoms – both by those who
have apparently recovered and those who have not yet developed symptoms. The
following hygiene measures also apply to preventing the spread of infection in the
workplace and schools.
Since the risk of introducing norovirus into the home, either via people or foods is
constant and may not be recognised until an outbreak of infection occurs within the
family, this means that good day-to-day hygiene including good food hygiene makes
sense.
General Hygiene
To prevent transmission of infection from an infected family member (or a family
member who may have been exposed to infection outside the home) to other family
members or to food.
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Good handwashing practice is the single most important infection control
measure. Hands should be thoroughly washed with soap and running water*. If
access to soap and running water is a problem, use an alcohol hand rub or hand
sanitiser**. In “high risk” situations where there is an outbreak of norovirus in the
home, it is suggested that handwashing followed by use of an alcohol
rub/sanitiser should be encouraged.
Hygienically clean surfaces in the bathroom and toilet, with particular attention to
washbasins, baths, toilet seats, toilet handles and showers. This can be achieved
by cleaning with a detergent cleaner followed by thorough rinsing under running
water, or when this is not possible, e.g. for toilet seats, toilet flush handles etc.,
using a disinfectant cleaner which is effective against norovirus***. If someone
has diarrhoea, toilets should be disinfected after each use.
Keep the infected person’s immediate environment hygienically clean. The most
important surfaces are those which come into contact with the hands, e.g. door
handles, telephones, bedside tables, bed frames, computer keyboards and TV
remote controls. To make these surfaces hygienically clean use a disinfectant
cleaner or disinfectant product which is effective against norovirus***, although,
for items such as computer keyboards which might be damaged, it is better to
make sure the family always wash their hands before using shared family
computers. In a busy household it is not always possible to keep hand contact
surfaces hygienically clean at all times. This is why it is so important to wash
hands as frequently as possible to break the chain of infection.
Cleaning cloths can easily spread norovirus around the home. They should be
hygienically cleaned after each use, particularly after use in the immediate area of
the infected person or the bathroom and toilet used by that person. This can be
done in any of the following ways:
- wash in a washing machine at 60C using a powder or tablet detergent
containing active oxygen bleach (see ingredients on back of pack)
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clean with detergent and warm water, rinse and then immerse in disinfectant
solution which is effective against norovirus for at least 20 minutes or as
prescribed
- clean with detergent and water then immerse in boiling water for 20 minutes.
Alternatively use disposable cloths.
Where floors or other surfaces become contaminated with faeces or vomit, they
should be hygienically cleaned at once:
- remove as much as possible of the excreta, from the surface using paper or a
disposable cloth, then
- apply disinfectant cleaner** which is effective against norovirus to the surface
using a fresh cloth or paper towel to remove residual dirt – then
- apply disinfectant cleaner** to the surface a second time using a fresh cloth or
paper towel to destroy any residual contamination.
- disposable gloves should be worn if in contact with faeces, and hands should
be washed after removing gloves.
After someone has vomited, if possible, vacate the room and ventilate it by
opening windows for a short time to disperse aerosol particles.
Clothing, bedlinen and towels should be regularly laundered using a laundry cycle
which will remove/destroy any pathogenic organisms. Either:
- for preference, wash at 60C or above, using a powder or tablet detergent
containing active oxygen bleach (see ingredients on back of pack).
- alternatively wash at 40C with a powder or tablet detergent containing active
oxygen bleach (see ingredients on back of pack)
Note: washing at 40C without the presence of active oxygen bleach will not
destroy bacteria and viruses
Do not share towels, facecloths, toothbrushes and other personal hygiene items
with the infected person.
Where young children are ill, or at particular risk:
- their handwashing, personal and toilet hygiene may need supervision
- nappies should be disposed of safely, or cleaned, disinfected and washed.
Contrary to popular perception, the faeces of babies can be highly infectious.
Where possible, infected people should stay in their own room and use their own
facilities, cutlery, crockery etc. Infected people should particularly avoid contact
with those who may be more vulnerable to infection, and their personal items.
Food and Kitchen hygiene
Rigorous food hygiene is important in preventing the spread of norovirus in the home.
Where there is an infected person in the home, food hygiene practices should focus
on preventing contamination of food, particularly ready-to-eat foods such as
sandwiches and salads. Where there is a suspected food source of the norovirus
outbreak in the home, food hygiene practice should focus on containing and
destroying the source, and preventing transfer to other foods.
 Infected people should try to stay away from the kitchen and should not prepare
food for others.
 Wash hands after handling food which may be contaminated and disinfect using
an alcohol handrub or sanitiser.
 Wash hands before handling ready to eat foods and disinfect using an alcohol
handrub or sanitiser.
 Hygienically clean all food contact surfaces, utensils and cloths after handling and
preparation of raw foods using a disinfectant cleaner which is effective against
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norovirus***. Hygienically clean all contact surfaces, utensils and cloths before
handling and/or preparing ready to eat foods.
Cook foods thoroughly.
Wash any foods such as fruit and vegetables to be eaten raw thoroughly under
clean running water.
Store foods carefully in a refrigerator or freezer. Ensure that raw foods are kept
separate from cooked foods.
*How to wash hands:
Handwashing “technique” is very important. Rubbing with soap and water lifts the
germs off the hands, but rinsing under running water is also vital, because it is this
process which actually removes the germs from the hands. The accepted procedure
for handwashing is:
 Ensure a supply of liquid soap, warm running water, clean hand towel/disposable
paper towels and a foot-operated pedal bin.
 Always wash hands under warm running water.
 Apply soap.
 Rub hands together for 15–30 seconds, paying particular attention to fingertips,
thumbs and between the fingers.
 Rinse well and dry thoroughly.
**In situations where soap and running water is not available an alcohol-based hand
rub or hand sanitiser should be used to achieve hand hygiene:
 Use an alcohol hand sanitizer containing not less than 62% v/v ethanol alone or
in combination with isopropyl alcohol at 10% v/v
 Apply product to the palm of one hand.
 Rub hands together.
 Rub the product over all surfaces of hands and fingers until your hands are dry.
Note:
 the volume needed to reduce the number of germs on hands varies by product. In
high risk situations where there is an outbreak in the home, handwashing
followed use of an alcohol rub/sanitiser should be encouraged.
Reducing any norovirus present on hands is best accomplished by thorough
handwashing with running water and plain soap. Washing with plain soap and water
reduces the number of microbes on hands via mechanical removal of loosely
adherent microorganisms. The efficacy of alcohol-based and other hand sanitizers
against norovirus remains controversial with mixed evidence depending on the
product formulation and evaluation methodology. Though 60–70% alcohol gels have
been demonstrated to have good effect against gram-positive and negative bacteria,
enveloped viruses, mycobacteria and fungi, WHO conclude that they have only
moderate effect against non-enveloped viruses, including rotavirus, adenovirus and
rhinovirus. The efficacy of alcohol hand santizers as used in the home setting is
given in a 2013 review, including data on new formulations, formulated to give
enhanced efficacy against norovirus.9
One very simple thing which people can do which can significantly reduce the risk of
disease is to avoid putting their fingers to their mouth.
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***Disinfectants and disinfectant cleaners
Make sure you use a disinfectant or disinfectant/cleaner such as a bleach-based
product, which is active against norovirus. The most usually recommended
disinfectant for norovirus is hypochlorite bleach. For more details on choosing the
appropriate disinfectant, see the IFH information sheet “Cleaning and disinfection:
Chemical Disinfectants Explained”. Consult the manufacturers’ instructions for
information on the “spectrum of action”, and method of use (dilution, contact time
etc). For bleach (hypochlorite) products, use a solution of bleach, diluted to 0.5% w/v
or 5000ppm available chlorine. Household bleach (both thick and thin bleach) for
domestic use typically contains 4.5 to 5.0% w/v (45,000-50,000ppm) available
chlorine. In situations where “concentrated bleach” is recommended a solution
containing not less than 4.5% w/v available chlorine should be used. Bleach/cleaner
formulations (e.g sprays) are formulated to be used “neat” (i.e. without dilution). It is
always advisable however to check the label as concentrations and directions for use
can vary from one formulation to another.
Other “facts about” sheets giving information on norovirus
 UK
National
Electronic
Library
on
Infections
(NELI)
http://www.neli.org.uk/IntegratedCRD.nsf/NeLI_Organisms1?OpenForm&Seq=1#_
RefreshKW_Bacteria
 Public
Health
England:
norovirus.
http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Norovirus/
 US
Centre
for
Disease
Control
and
Prevention.
http://www.cdc.gov/norovirus/index.html
 European Centre for Disease Control and Prevention: norovirus
http://www.ecdc.europa.eu/en/healthtopics/norovirus_infection/Pages/index.aspx
IFH Guidelines and Training Resources on Home Hygiene
 Guidelines for prevention of infection and cross infection the domestic
environment. International Scientific Forum on Home Hygiene. Available from:
http://www.ifh-homehygiene.com/best-practice-care-guideline/guidelinesprevention-infection-and-cross-infection-domestic
 Guidelines for prevention of infection and cross infection the domestic
environment: focus on issues in developing countries. International Scientific
Forum on Home Hygiene. Available from: http://www.ifh-homehygiene.org/bestpractice-care-guideline/guidelines-prevention-infection-and-cross-infectiondomestic-0
 Recommendations for suitable procedure for use in the domestic environment
(2001). International Scientific Forum on Home Hygiene. http://www.ifhhomehygiene.org/best-practice-care-guideline/recommendations-suitableprocedure-use-domestic-environment-2001
 Home hygiene - prevention of infection at home: a training resource for carers and
their trainers. (2003) International Scientific Forum on Home Hygiene. Available
from:
http://www.ifh-homehygiene.com/best-practice-training/home-hygiene%E2%80%93-prevention-infection-home-training-resource-carers-and-their
 Home Hygiene in Developing Countries: Prevention of Infection in the Home and
Peridomestic Setting. A training resource for teachers and community health
professionals in developing countries. International Scientific Forum on Home
Hygiene. Available from: www.ifh-homehygiene.org/best-practice-training/homePage 7/8
hygiene-developing-countries-prevention-infection-home-and-peri-domestic. (Also
available in Russian, Urdu and Bengali)
This fact/advice sheet was last updated in 2014
References
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5
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Bloomfield SF. Exner M, Signorelli C, Nath KJ, Scott EA. 2012. The chain of
infection transmission in the home and everyday life settings, and the role of
hygiene in reducing the risk of infection.
http://www.ifh-homehygiene.com/best-practice-review/chain-infectiontransmission-home-and-everyday-life-settings-and-role-hygiene
The Longitudinal study of infectious intestinal disease in the UK (IID2 study):
incidence in the community and presenting to general practice Tam CC,
Rodrigues LC, Viviani L, et al. Gut (2011). doi:10.1136/gut.2011.238386.
Scallan E, Hoekstra RM, Angulo FJ, et al. Foodborne illness acquired in the
United States—major pathogens. Emerg Infect Dis 2011;;17:7–15.
Updated Norovirus Outbreak Management and Disease Prevention
Guidelines 2011
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6003a1.htm?s_cid=rr6003a1_e
The European Union Summary Report on Trends and Sources of Zoonoses,
Zoonotic Agents and Food-borne Outbreaks in 2010. Scientific report of EFSA and
ECDC Downloadable from http://www.efsa.europa.eu/en/efsajournal/doc/2597.pdf
The European Union Summary Report on Trends and Sources of Zoonoses,
Zoonotic Agents and Food-borne Outbreaks in 2010. Scientific report of EFSA and
ECDC Downloadable from http://www.efsa.europa.eu/en/efsajournal/doc/2597.pdf
Hall AJ, Wikswo ME, Manikonda K, Roberts VA, Yoder JS, Gould LH. Acute
gastroenteritis surveillance through the National Outbreak Reporting System,
United States. Emerg Infect Dis. 2013. http://dx.doi.org/10.3201/eid1908.130482 .
Norovirus infection in the home and the role of hygiene – an update. 2008.
International Scientific Forum on Home Hygiene. Available from: http://www.ifhhomehygiene.org/review/norovirus-infection-home-and-role-hygiene
Bloomfield SF, Scott EA A risk assessment approach to use of antimicrobials in
the home to prevent spread of infection American Journal of Infection Control
2013; 41: (5, Suppl) A1-A10, In Disinfection, Sterilization and Antisepsis: Current
Issues, New Research and New Technologies. Edited by William A. Rutala and
David J. Weber
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