Noro virus Information and Advice
Noro virus, also known as Norwalk and the winter vomitting bug is highly contagious accounting for over 50% of epidemic, viral gastroenteritis cases. Of the calicivirdae family of viruses it is prevalent during the winter and an ongoing problem for hotels, cruise ships and care homes that accommodate large numbers of people who share public areas and facilities.
The virus is self limiting and most people make a full recovery without need for medical assistance. After recovering from infection, immunity is usually short lived and incomplete. Immunity from one strain of the virus will not give immunity to another. Sufferers can expect to be immune to the strain that they were ill with for between three and six months. People often underestimate how virulent NV actually is and are convinced that they cannot catch it twice so therefore they must have food poisoning.
High risk foods such as salad and ready to eat foods are more likely to harbor the virus especially if handled by an infected person. Oysters harvested from contaminated beds have also been identified as a vehicle for the virus. I would ensure that a strict sickness policy is in place and that staff receive appropriate training with regard to food preparation. Staff and supervisors must be vigilant, especially during an outbreak in order to limit the scope of the outbreak.
The virus is common during cold weather due to the fact that people tend to congregate indoors when the weather is cold. Lower temperatures and less sunlight also aid the virus during the winter as it takes longer for the virus to die on contaminated surfaces such as door handles and hand rails. Less sunshine also lowers the human immune system making it harder to fight off a viral infection.
Large scale norovirus outbreaks tend to occur where people group in a confined space for prolonged periods of time. This is why cruise ships, hospital wards, hotels and care home are hard hit by noro virus outbreaks. Accommodation providers will have to deal with the fact that the ill people will not be able to leave until they are better, will need to be confined in order to protect other people and also that paying guests will be extremely irate.
Symptoms include projectile vomiting, stomach cramps, high temperature, diarrhoea and nausea. The onset of symptoms is usually 12 to 24 hours after infection. There is no specific cure for infected persons, the virus must be allowed to run its course. Most people make a full recovery within a few days. The most important thing is to ensure clients take on plenty of fluids to prevent dehydration. To facilitate this I recommend regular visits by staff to rooms to replenish supplies.
Aerosolization of the virus can occur in some situations, for example when a person is sick or when the toilet is flushed. The virus is only airborne for a short time however viral particles can land on surfaces and fabrics in the immediate area. Even a carrier bag has been found to cause an outbreak.
Norovirus is non-cultivatable, it cannot be reproduced in the laboratory making it difficult to create a vaccine although many organisations are working on this. Vaccination has also been hampered by the ability of the genome to mutate and allow a new strain to develop.
How can I get infected with the bug
Noro virus can be transmitted from person to person, via contaminated food or water and aerosolisation of the virus which subsequently contaminates surfaces and fabrics. Around 70% of people who are within a 3 meter radius of a vomiting episode by an infected person can become poorly. However the viral particles will land on the surrounding fabrics and hard surfaces which put other people who use this area at risk. Hard surfaces can remain a hazard for several days so it is crucial that a decontamination procedure is in place. Affected areas should not be used for at least 48 hours after a thorough clean and sanitization has taken place.
The organism can affect all ages but is generally more severe in young children and the elderly. These are also the most vulnerable groups in society and often at risk of inadvertent exposure to the illness. Whilst senior citizens may be exposed in a residential establishment or guest house, children may come into contact with the virus at school or day nursery.
Controlling the virus
The most effective way to control Norovirus, limit its spread and reduce the chances of becoming infected, is hand-washing and thorough hygiene. Hands should be washed with soap and water and you should not put your hands near your mouth if they have not been washed. This will prevent viral particles from your hands being ingested and also reduce the risk of cross contamination of surfaces that you touched.
Surfaces should be sanitized with a domestic bleach solution of 5 tablespoons of bleach per litre of water. Alcohol based cleaning agents and detergent are less effective in controlling norovirus as the virus does not have a lipid envelope. Hand gels should therefore not be used as a substitute for regular hand washing with soap and water. It is very important that chefs and kitchen staff are aware of this.
Find out more about noro virus - Noro virus links
- Useful Leaflet on Norovirus
Document from Glasgow and Clyde NHS regarding the control of a noro virus outbreak.
- Norovirus Outbreak Control Guidelines
Health Protection Agency HPA document on managing an outbreak in social care situations.
- Questions and answers on noro virus
Eastbourne council document answering FAQ about noro virus.
- Noro virus in hotels
Documnet from Eastbourne Council regarding noro virus outbreaks in hotels,
- Norovirus Management Protocol for Cruise Ships
Full management protocol specifically for implementation during Norwalk virus outbreaks on cruise ships.
- NHS Direct
Information from NHS Direct regarding treatment and prevention of Norwalk Virus.
Prevails during cold weather
The virus is more common in the winter and rapidly spread indoors
What is Noro virus?
It is a viral infection, not a bacterial infection and is therefore highly contagious. It is also known as Small Round Structured Virus (SRSV). It is present in the stools of an infected person once the virus has been ingested. During the incubation period an infected person may not display symptoms but can infect other people. People are at the most contagious from the onset of symptoms up until at least 24 hours after the symptoms have passed and are advised not to handle food for at least 48 hours after the last symptoms passed. The virus can still be shed in peoples stools for several weeks after recovery.
Isolate infected people
What are the Symptoms of Noro virus?
Projectile vomiting, watery diarrhoea and nausea
The onset of symptoms can be from 12 to 48 hours after infection. Symptoms will generally be the sudden onset of nausea accompanied by projectile vomiting and watery diarrhoea. Some people may also experience aching limbs, fever, headache and raised temperature. Vomiting can often be sudden meaning that it often occurs in a public space, putting those in the immediate vicinity at risk of infection. You should avoid going to the doctors with norovirus symptoms as this will spread the virus about. You can get information and advice about noro virus by telephoning NHS Direct on 0845 46 47. If symptoms persist for more than 48 hours you may be advised to see your GP. You should call the surgery first rather than just turning up. The virus is self limiting and most people make a full recovery within a few days. Recovering person remain infectious for several days after symptoms have passed and will pass the virus in stools for two weeks after recovery. Aches and pains can be relieved with over the counter medicines and using diarrhoea relief will not prolong infection.
image: Daily Mail
Where does the virus come from?
Norwalk, Ohio after an outbreak of viral gastroenteritis at Bronson Elementary School in November 1968. These viruses account for over half of all reported outbreaks of viral gastroenteritis each year. The viruses only affect humans and are characterised by large outbreaks in the community.
Once you have ingested the viral particles they will make their way to your stomach. The virus does not do anything to cause illness until it reaches the small intestine. Here it attaches itself to the lining of the small intestine and releases bio genes. The bio genes take control of the cells and create more copies of the virus.
There is no specific cure or treatment other than to drink plenty of fluids to prevent dehydration. An affected person should make a full recovery within 1 or 2 days, once the virus has run its course. Medical attention is rarely required except in the most serious of cases. Special attention should be paid to young children and the elderly who can be harder hit by the symptoms and dehydrate more quickly.
The act of vomiting is a secondary response to the virus and doesn't actually help you to get rid of it. It is a natural response from your body and may make you feel better but the only way to get better is for your body to create the antibodies required to deactivate the virus. People with healthier immune systems are more likely to overcome the virus quickly.
It is also safe to take diarrhea relief such as Imodium. It will relieve the symptoms and does not keep the virus inside your body and prolong the illness. You will only be cured when your immune system has "switched off" the virus. Immunity is strain specific and short-lived.
Contamination of surfaces
Sanitise preparation surfaces to ensure that viral particles can't be transferred to food.
How do you get Noro virus?
The only way to catch norovrus is the faecal-oral route. You have to ingest the viral particles contained in the faeces or vomit of an infected person. You cannot breathe the virus in. However it is possible to swallow viral particles if an infected person is sick near to you as the spray droplets may come up and touch your mouth or nose and enter your body. Up to 70% of people within three mettre of a vomiting episode can become infected via aerosol droplets of the virus. The airborne viral particles may also land on fabrics and surfaces, contaminating them with the virus. One vomiting episode may contain 30,000 000 viral particles whereas it only requires the ingestion of between 10 and 100 particles to become infected. Deep cleaning and disinfection of theses surfaces is vital to control the spread of the virus and these areas must be closed to the public for at least 48 hours.
Noro virus can often be traced back to a single food handler whether in a private household or workplace.
When you touch a surface or door handle, you are also touching whatever the last person left on there. If they have not washed their hands after using the toilet and are infected, they will leave viral particles on the surface. You cannot get the virus by simply touching an infected surface, you would need to put your hands on your mouth or nose in order to ingest the virus. It is therefore of utmost importance that frequent hand washing takes place, especially if you are about to eat or prepare food.
Hand gels are not a substitute for good hand washing with soap and water as the virus does not have a lipid envelope. Washing hands helps remove the virus from your hands and wash it down the sink. Disposable paper towels should be used to prevent passing the virus on to other people. Using paper towel or tissue to open the door will also help you from touching an infected surface as you leave the bathroom.
Poor hygiene spreads norovirus
Faecal-oral route, you have to swallow the viral particles in order to become infected.
Control of an Outbreak
Isolate infected persons and meticulous hygiene
Outbreak control measures are different depending on the type of operation. In broad terms, infected persons should be isolated for the duration of the illness and for at least 24 hours after symptoms cease. Contact with other people should be avoided in order to reduce the potential for the virus to spread. In hotels affected persons should be confined to their rooms as should anybody who is sharing the room with them as this will reduce the spread of the virus. The person or persons sharing the room should be discouraged from using public spaces and must not use public toilet facilities. In hospital and care facilities, visiting should be discouraged unless absolutely essential. Patients and residents should be isolated and transfer and admissions must be halted.
Designated persons should use the correct, disposable protective equipment and cleaning materials when looking after affected persons. Dirty laundry should be bagged separately in the affected area and sprayed with a sanitiser solution whilst still in the room. All disposable cutlery, plates, gloves and clothes should also be bagged whilst in the affected area and the bag sprayed with sanitiser. These bags can them be removed for disposal / onward transfer. Items for cleaning should be clearly visible as hazardous which can be done by using RED refuse sacks.
To minimise the risk of contamination, cleaning and care duties should be carried out by designated persons who are not also tending to people who are well. Virus particles may be present on the hands and clothing of the staff member and could be transferred to other people who they are in close contact with.
The most important measure in the control of the virus is to maintain high levels of hand hygiene and ensure that all touch surfaces are regularly sanitised with a chlorine based solution. This reduces the potential for the virus to spread to others. Alcohol hand gel is not effective against Norovirus and is not a substitute for hand washing which washes the viral particles down the sink.
A mild bleach solution of five tablespoons of bleach to one litre of water, should be used to clean affected hard surface areas and the bathroom facilities of affected people. Care should be taken to clean the flush handle and other touch surfaces where viral particles may have landed. Hot water and detergent should be used to clean sickness on carpets and fabrics and a window left open to allow it to dry.
Soiled bed linen and other fabrics should not be hand washed as water droplets containing the virus may be dispersed into the air and swallowed by the handler. Dirty linen should be pre-washed in a washing machine and then washed at the highest temperature tolerated by the fabric. A full wash at 60` will be enough to kill the virus.
Affected food handlers should refrain from work for 48 hours after symptoms have passed to prevent contamination of food. All food handlers must up their hand washing routine to prevent possible contamination of food. Touching contaminated surfaces and then handling food could cause illness if the food is eaten so it is important to take care when handling food, even if not ill yourself.
Noro virus Prevention
Hand washing will help protect you and your family
You cannot always avoid getting Noro virus, but frequent and thorough hand washing with soap and water is the most effective way to avoid infection and the possible infection of others. Always wash your hands after using the toilet and before preparing food. Help protect your family by wiping surfaces with a household bleach solution, using disposable towels for cleaning. Avoid sharing towels and flannels and ensure that any contamimated bed linen is washed separately on a hot wash.
You must not prepare food for other people for at least 48 hours after symptoms have passed. Contact with other people should also be avoided and you must not visit people in hospital during this time as the virus is more serious and more easily spread amongst people who are already ill.
Prevention of norovirus
Wash hands regularly with soap and water. Avoid touching your mouth and nose with your hands.
Disinfection against noro virus
As norovirus cannot be reproduced in the laboratory, feline calicivirus (FCV) is often used as a surrogate when testing the effectiveness of chemicals against the virus. Sodium Hypochlorite is considered the "Gold Standard" when disinfecting hard surfaces against the virus but has the disadvantage of being damaging to soft furnishings such as carpets and fabrics.
The best way to clean fabrics and carpets is to first remove any matter, which may be harbouring the virus, by using hot water and detergent. A disinfection process via steam cleaning should then be followed. Fogging of affected areas is a possible additional measure but is not a substitute to thorough cleaning and sanitising of surfaces.
Sodium hypochlorite is the active ingredient in many products effective against norovirus. In the Guidance for the Management of Norovirus Infection on Cruise Ships document above, you will find product data regarding norovirus disinfection agents. Sodium Hypochlorite requires a contact time of 1 minute at 0.1% (1000 ppm) concentration. Chlorine bleach has a concentration of 5% chlorine and can therefore be diluted 50-1. When bleach is diluted the concentration begins to decline and it is therefore advisable to make up fresh solutions on a daily basis.
Top norovirus tips
- Do not visit your GP or A&E, you will put other people at risk
- Use NHS Direct and symptom checker to manage your treatment
- Don't prepare food whilst you are ill or recovering from the norovirus disease
- Drink plenty of fluid to avoid dehydration
- Wash your hands and ensure other people also wash their hands
- Use a domestic bleach solution to clean toilets, handles and flushes
- Use separate towels
- Don't visit other people in hospital or care facilities
Contact NHS Direct on 0845 46 47 if you are concerned about norovirus. You can also use the NHS symptom checker if you are feeling unwell.