Noroviruses
Noroviruses, often referred to as Norwalk-like viruses, are a group of highly contagious viruses that primarily cause acute gastroenteritis, leading to symptoms such as sudden nausea, vomiting, abdominal cramps, and watery diarrhea. Commonly mistaken for the "stomach flu," norovirus infections can occur through contaminated food or water, direct person-to-person contact, or contact with contaminated surfaces. The illness typically lasts between twelve to sixty hours, and while most healthy individuals recover fully without long-term effects, vulnerable populations like the elderly and young children may face serious complications like dehydration.
Noroviruses are particularly prevalent in crowded environments such as schools, hospitals, and cruise ships, where outbreaks can spread rapidly. The virus is notably resistant to various environmental conditions, making prevention challenging. Effective measures to combat norovirus transmission include practicing good hygiene, such as frequent hand-washing, and ensuring proper food safety practices. Despite the high incidence of norovirus infections, there are no specific antiviral treatments available, and antibiotics are ineffective since the virus is not bacterial. Understanding the transmission routes and symptoms of noroviruses can help individuals and communities implement better preventive strategies to minimize outbreaks.
Noroviruses
ALSO KNOWN AS: Norwalk-like viruses
ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, immune system
DEFINITION: A family of viruses that cause acute gastroenteritis
CAUSES: Viral infection transmitted through contaminated food or water, fecal-hand-oral contamination, direct person-to-person contact, or direct contact with contaminated surface
SYMPTOMS: Sudden onset of nausea, vomiting, abdominal cramps, and watery diarrhea; may also include headache, fever, chills, and muscle pain
DURATION: Twelve to sixty hours
TREATMENTS: None; prevention through food safety measures (proper handing) and good hygiene (frequent hand-washing, germicides)
Causes and Symptoms
Noroviruses, also known as Norwalk-like viruses (NLV), are members of the family Caliciviridae and are the leading cause of nonbacterial acute gastroenteritis outbreaks in the United States. According to the Centers for Disease Control and Prevention (CDC), noroviruses are suspected of causing from nineteen to twenty-one million cases of acute annually with an estimated 900 deaths each year. Often, norovirus-caused gastroenteritis is thought to be “stomach flu,” but it is not related to influenza, a respiratory illness caused by the virus. Norovirus infection is also commonly referred to as “food poisoning,” although there are other numerous causes of food poisoning. Noroviruses are not related to or parasites that can cause gastroenteritis.
The illness associated with a norovirus infection lasts twelve to sixty hours and is characterized by a sudden onset of nausea, vomiting, abdominal cramps, and watery diarrhea. Vomiting is more prevalent among children, whereas adults tend to experience diarrhea. Additional symptoms, including headache, fever, chills, and myalgia (muscle pain), are also reported. Although a norovirus causes a self-limited acute gastroenteritis, the elderly, children, and those with severe underlying medical conditions are at increased risk for complications as a result of volume depletion, dehydration, and electrolyte disturbances. Although rare, severe dehydration caused by norovirus gastroenteritis can be fatal. Hospitalization of otherwise healthy adults infected with a norovirus infection is rare.
The after exposure to a norovirus is twelve to forty-eight hours. The virus is transmitted by a fecal-hand-oral contamination route, directly from person to person, through contaminated food or water, or by direct contact with a contaminated surface. One of the main sources is the diapers of infants with diarrhea. Aerosolized vomit has also been implicated as a transmission mode. Noroviruses are very contagious and can spread rapidly throughout closely populated environments: Schools, hospitals, restaurants, amusement parks, fairgrounds, summer camps, and cruise ships are especially susceptible to mass infections. However, any place that food or drink is served, including the home environment, is susceptible to a norovirus infection. Because of high rates of infection and the persistence of noroviruses in the environment, transmission is difficult to control through routine sanitary procedures. People infected with a norovirus are contagious from the moment that they begin feeling symptoms to at least three days after recovery. In some cases, infected individuals have been contagious two weeks after recovery.
Most people infected with noroviruses recover in twenty-four to forty-eight hours, with no long-term health effects related to their infection. No evidence suggests that infected persons can become long-term carriers of the virus, but it is essential for those recovering from an infection to use good hand-washing and other hygienic practices.
Treatment and Therapy
Outbreaks of norovirus gastroenteritis can occur in multiple settings. According to the Centers for Disease Control and Prevention, between August 1, 2023 and March 12, 2024, there were 998 confirmed norovirus outbreaks in the United States, higher than the 998 outbreaks reported during the previous years. While person-to-person spread of the disease extends norovirus outbreaks, the initial event is often the contamination of a common source such as a surface or food or water. As a result, efforts to prevent an initial contamination and subsequent transmission help to prevent the occurrence and spread of norovirus gastroenteritis outbreaks.
Food contamination by food handlers is the most frequent transmission agent. Any food item has the potential to be infected with a norovirus through fecal contamination, and certain foods show a higher concentration of infections. Shellfish tend to concentrate noroviruses in their tissues if they live in contaminated waters in which fecal waste is either dumped overboard from ships or released from shoreline sewage systems. Ready-to-eat foods that require handling but no subsequent cooking also pose a risk. Noroviruses are relatively resistant to environmental change and can survive temperatures as high as 140 degrees Fahrenheit (60 degrees Celsius) and can survive in up to 10 parts per million of chlorine, well in excess of levels in public water systems. A norovirus infection can occur as a result of the ingestion of contaminated water, including municipal water, well water, stream water, commercial ice, lake water, and swimming pools.
Noroviruses can be spread person-to-person by direct fecal-oral contact and airborne transmission. This is the most effective way that the virus spreads in populations in close proximity, such as people in nursing homes and on cruise ships. The most effective means of stopping the transmission of a norovirus is by frequent hand-washing with soap and hot water. It is recommended that all surfaces be lathered with soap vigorously for ten seconds, then rinsed thoroughly under moving water. A mask should be worn by anyone cleaning areas contaminated with feces or vomitus. Soiled linen and clothes should be handled carefully and with a minimum of agitation. Soiled surfaces should be cleaned with a germicidal product containing at least 10 percent bleach.
Neither a specific antiviral treatment nor a has been developed for noroviruses. A norovirus infection cannot be treated with antibiotics because it is not caused by bacteria. Because there are many different strains of norovirus, developing an individual long-lasting immunity is difficult. As a result, norovirus infections can recur throughout a person’s lifetime. As a result of genetic factors, some people are more likely than others to be infected and to develop severe symptoms.
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