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Noroviruses are a group of viruses that cause the “stomach flu,” or gastroenteritis (GAS-tro-en-ter-I-tis), in people. The term norovirus was recently approved as the official name for this group of viruses. Several other names have been used for noroviruses, including:
Viruses are very different from bacteria and parasites, some of which can cause illnesses similar to norovirus infection. Like all viral infections, noroviruses are not affected by treatment with antibiotics, and cannot grow outside of a person’s body. What are the symptoms of illness caused by noroviruses? The symptoms of norovirus illness usually include nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people additionally have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. In most people the illness is self-limiting with symptoms lasting for about 1 or 2 days. In general, children experience more vomiting than adults. Most people with norovirus illness have both of these symptoms. What is the name of the illness caused by noroviruses? Illness caused by norovirus infection has several names, including:
How
serious is norovirus disease? How do people become infected with noroviruses? Noroviruses are found in the stool or vomit of infected people. People can become infected with the virus in several ways, including:
Persons working in day-care centers or nursing homes should pay special attention to children or residents who have norovirus illness. This virus is very contagious and can spread rapidly throughout such environments. When do symptoms appear? Symptoms of norovirus illness usually begin about 24 to 48 hours after ingestion of the virus, but they can appear as early as 12 hours after exposure. Are noroviruses contagious? Noroviruses are very contagious and can spread easily from person to person. Both stool and vomit are infectious. Particular care should be taken with young children in diapers who may have diarrhea.How long are people contagious? People infected with norovirus are contagious from the moment they begin feeling ill to at least 3 days after recovery. Some people may be contagious for as long as 2 weeks after recovery. Therefore, it is particularly important for people to use good handwashing and other hygienic practices after they have recently recovered from norovirus illness. Who gets norovirus infection? Anyone can become infected with these viruses. There are many different strains of norovirus, which makes it difficult for a person’s body to develop long-lasting immunity. Therefore, norovirus illness can recur throughout a person’s lifetime. In addition, because of differences in genetic factors, some people are more likely to become infected and develop more severe illness than others. What treatment is available for people with norovirus infection? Currently, there is no antiviral medication that works against norovirus and there is no vaccine to prevent infection. Norovirus infection cannot be treated with antibiotics. This is because antibiotics work to fight bacteria and not viruses. Norovirus illness is usually brief in healthy individuals. When people are ill with vomiting and diarrhea, they should drink plenty of fluids to prevent dehydration. Dehydration among young children, the elderly, the sick, can be common, and it is the most serious health effect that can result from norovirus infection. By drinking oral rehydration fluids (ORF), juice, or water, people can reduce their chance of becoming dehydrated. Sports drinks do not replace the nutrients and minerals lost during this illness. Can norovirus infections be prevented? You can decrease your chance of coming in contact with noroviruses by following these preventive steps:
Persons who are infected with norovirus should not prepare food while they have symptoms and for 3 days after they recover from their illness. Noroviruses are a group of viruses that cause gastroenteritis in people. These viruses are part of a family called caliciviruses. While animals do carry other kinds of caliciviruses, they are not believed to carry noroviruses. The term norovirus was approved as the official name for this group of viruses in 2002. Previously, they were called Norwalk-like viruses. Noroviruses are commonly found throughout North America and are very infectious. Noroviruses can survive on practically any surface including door handles, sinks, railings and glassware. They occur throughout the year but are more common in winter and affect all age groups. What causes infection with noroviruses?People carry noroviruses, which are found in the stool or vomit of infected individuals, while they are ill and up to at least three or four days after recovery. Some people may be contagious for as long as two weeks after recovery. People are usually infected with noroviruses by direct contact with a person who is ill or has recently been ill or through indirect contact by touching surfaces contaminated with the virus, like door handles or by eating contaminated food or drinking contaminated water. The virus is able to survive relatively high levels of chlorine and varying temperatures and can survive on hard surfaces in the environment for up to 12 hours. It has been found to survive on contaminated carpet for up to 12 days. Noroviruses are easily transmitted in environments where people are in close contact, including schools, day-care centres, long-term care facilities, healthcare facilities and cruise ships. What are the symptoms of illness caused by noroviruses?The symptoms of norovirus illness include nausea, vomiting, diarrhea and stomach cramps. Sometimes, people may have a low-grade fever, chills, headache, muscle aches and fatigue. The illness often begins suddenly, about 24 to 48 hours after exposure. How long do the symptoms last?In most healthy people, acute diarrhea and vomiting usually last eight to twelve hours, and people normally recover in 48 hours. Symptoms may last longer in some people. How can norovirus infections be prevented?You can reduce the risk of norovirus infections by:
How long are people infectious?People infected with norovirus are contagious from the moment they begin feeling ill to at least three or four days after recovery. Some people may be contagious for as long as two weeks after recovery. Good hygiene standards, including frequent hand washing, are very important during this period. What is the treatment for norovirus infection?There is no preventative treatment (vaccine or antiviral medication) for noroviruses and they cannot be treated with antibiotics because antibiotics fight bacteria, not viruses. However, healthy people normally recover on their own in about 48 hours. Those suffering from illness should drink plenty of fluids to prevent dehydration - a possible serious health effect of norovirus infection. People should drink juice or water to reduce their chance of becoming dehydrated. Sports drinks are not recommended because they do not replace the nutrients and minerals lost during illness. If serious dehydration occurs, the ill person may require re-hydration in hospital. Are noroviruses dangerous?Generally, noroviruses cause unpleasant but self-limiting, gastrointestinal symptoms, such as diarrhea and vomiting. The risk of more severe illness, including dehydration, is likely to occur in the very young, the elderly and those with weakened immune systems. Have people died of noroviruses in Canada?Deaths have occurred in long-term health care facilities during norovirus outbreaks, but it is difficult to say to what extent norovirus caused death in already frail or sick people. It would be considered a contributing factor but not the cause of death. Does the Public Health Agency keep track of noroviruses across the country?The Agency monitors for gastrointestinal disease cases and outbreaks through national surveillance programs. Is this year worse than past years?We have recorded 300 to 400 outbreaks this year and this reflects increased reporting since 2002. This increase likely is partly linked to more incidents and partly linked to better reporting. How many outbreaks do we see in Canada in a year?At present we are receiving 300 to 400 outbreaks reported each year since 2002. This compares with less than 100 outbreaks in previous years (1998-2001). The increase is likely due partly to increased numbers of outbreaks and improved reporting. What's the difference between a case and an outbreak?A case refers to illness in one person whereas an outbreak refers to two or more people linked by a common exposure within a specific time frame. Norwalk-like viruses, also known as noroviruses, are common causes of viral enteritis, accounting for over 66% of the estimated cases of foodborne illnesses in the United States each year. Gastroenteritis outbreaks in the U.S. between the years 1996-2000 have been caused by noroviruses in 39% of restaurant and catered events outbreaks, 30% of outbreaks in nursing homes, 12% of those in schools and day care centers, 10% of vacation outbreaks, and 9% miscellaneous outbreaks. Its implication among cruise ship outbreaks has brought this more obscure pathogen into the limelight in recent months. Symptoms Noroviruses are called such because there is not just one, but rather a series of four, small RNA-viruses that are implicated in the transmission of disease. They are environmentally stable and will survive water chlorination and a wide temperature range, from freezing and heating to 140° F (60°C). Onset of illness occurs within 12-48 hours and lasts approximately 12-60 hours. Symptoms include nausea, vomiting, abdominal cramps, and diarrhea. Transmission-Foodborne Food contamination by infectious food handlers is the most common cause of norovirus-related gastroenteritis outbreaks. Transmission usually occurs from exposure to fecally contaminated food or water resulting from failure to wash hands properly after using the restroom. Shellfish, in particular oysters and clams, have been implicated due to the ability of noroviruses to concentrate in their tissues or to contaminate waters where the shellfish are harvested. Of particular concern is transmission through ready-to-eat foods, which do not require cooking, such as salads and deli sandwiches. Because only a very low exposure is needed to result in a substantial outbreak, attention must be given to preventive actions. These include emphasis on frequent handwashing, exclusion of ill foodworkers from the workplace, properly cleaning and disinfecting surfaces and limiting possible contamination of ready-to-eat foods by either customers or foodhandlers. Transmission-Person-to-Person Person-to-person spread of noroviruses occurs by direct fecal-oral and airborne transmission. This has been a factor in institutional settings such as nursing homes, day care centers and on cruise ships. Wearing masks can be effective in protecting individuals, such as hospital or nursing home staff, who clean areas contaminated by feces or vomitus. For hospital and nursing home staff, protective measures include properly disinfecting surfaces of known contamination, taking special care in laundering soiled linens, and wearing of masks by staff that clean areas contaminated with feces or vomitus. Transmission-Water Although infrequent, gastroenteritis outbreaks have been associated with fecal-contaminated municipal water, well water, stream water, commercial ice, lake water and swimming pool water. In such instances, high level chlorination might be required for adequate disinfection. Bottom Line Although it is impossible to completely eliminate possible exposure to noroviruses in our environment, we can minimize our risk by taking the following actions:
If you or your family comes down with a norovirus infection or the "flu":
Noroviruses are the primary cause of more serious infections that occur in tropic zones of the earth. However, the populace of the United States is not free of Noroviruses infections. In the United States, poorer populations are most commonly affected with native-born infections; however, no one is immune. For example, raccoons or possums can use playgrounds as noctural pathways, leaving behind ascarid eggs that can later infect children. The increase in immigration and world travel has complicated regional parasitic infections. Today, it is not unusual for the general medical practitioner to be confronted with an exotic disease. Both domestic and wild animals may act as reservoirs for parasites, and some can transmit infections to humans. A disease caught by a human from an animal is called a zoonosis. Examples of zoonotic diseases include hydatid disease or Toxomplasma gondii. Hydatid disease is caused by larval tapeworms that hatch from eggs ingested from dog feces (handling an infected dog and/or its feces, then touching the mouth). Toxoplasma gondii is normally a parasite of cats and rodents. It can be transmitted to humans, and it is known to cause birth defects. Parasitic infections cause damage by physical trauma. They also cause damage by destroying cells, tissues, or organs by mechanical or chemical means. Parasites also divert the host's nutritive substances. Some parasites also produce toxins that further damage the host. This site focuses primarily on those Noroviruses of interest to humans, either directly or because of economic importance to livestock. The information is divided into these catagories. Enjoy!
Harmful Bacteria
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