Different cases of acute gastroenteritis occurred, about a fortnight ago, in the Passo del Tonale area, between Lombardy and Trentino Alto Adige. There cause could be Norovirustraces of which were detected in the samples taken from the aqueduct: in the name of “the principle of maximum precaution”, it was immediately issued by the mayor of Ponte di Legno, who The use of water for food purposes is prohibited. It has been in the area for about ten days It is forbidden to drink tap water and use it to wash fruit and vegetables.
“Norovirus can appear in water in exceptional cases and can be eradicated by sanitizing the network”, he specified the mayor Ivan Faustinelliexplaining that “as soon as the results of the counter-analysis are available, all necessary measures will be adopted as quickly as possible”.
What is Norovirus
But what is the microorganism that triggered the alert in the area? Isolated and discovered in 1972, noroviruses belong to the Caliciviridae family, single-stranded RNA viruses, and represent one of the most widespread agents of acute gastroenteritis of non-bacterial origin – explain the experts of the Higher Institute of Health on the Epicentro website – thus constituting a serious problem in the field of food safety. Infections caused by norovirus occur mainly in community settings, in hospitals, nursing homes, schools or, typically, in confined environments, such as commercial and cruise ships. Not cultureable in the laboratory, noroviruses have posed some diagnostic problems in the past. Until a few years ago, in fact, it was possible to identify them only by observation under an electron microscope, given their tiny dimensions, or by measuring the presence of antibodies in the blood. For about ten years, rapid diagnostic tests have been developed with the use of molecular markers or using commercial Elisa tests for the detection of the virus from biological samples. To date, three genogroups of noroviruses are known: GI, GII and GIV capable of infecting humans.
Symptoms and course
The incubation period of the virus is 12-48 hours, while the infection lasts from 12 to 60 hours. The symptoms – experts highlight – are those common to gastroenteritis, namely nausea, vomiting, especially in children, watery diarrhea, abdominal cramps. In some cases, a slight fever also occurs. The disease usually has no serious consequences, and most people recover in 1-2 days without complications. Normally, the only measure is to drink plenty of fluids to compensate for dehydration resulting from vomiting and diarrhea. In particular, dehydration can represent a more serious complication for children, the elderly and subjects with precarious metabolic or cardiovascular balance, and may therefore require some medical attention. There is no specific treatment against norovirus, nor a preventative vaccine. The mechanisms of immunization against norovirus are little known, and according to the CDC, immunity lasts only a few months: the same individual can therefore be infected by the virus several times during his life.
How is it transmitted?
It is a highly infectious pathogen and 10 viral particles are enough to give rise to an infection. Given their persistence in the environment, which allows their replication and spread even for two weeks after the initial infection, noroviruses are difficult to control and it is therefore necessary to apply rigorous health measures to prevent and contain them. Transmission occurs directly from person to person, via fecal-oral or via aerosol, or via infected water or food, but also by contact with contaminated surfaces.
In most documented cases, transmission occurred through the consumption of contaminated water or food. In the latter case, the food could be contaminated at the source, by infected water, both in the case of seafood (particularly oysters) and fresh vegetables or berries. In many cases, contamination has been attributed to water storage tanks or swimming pools and fountains. Outbreaks are often associated with the consumption of raw seafood, salads, berries, contaminated water, cold foods, sprouts, herbs and spices.
How to prevent the virus
The only effective form of control of norovirus is the implementation of strict hygiene measures in the handling and distribution of food and drink. Noroviruses are quite resistant in the environment, surviving temperatures above 60 degrees C and even in the presence of chlorine, normally used to disinfect drinking water. Furthermore, they remain in the feces of infected people for at least 72 hours after recovery. It is therefore clear that only very stringent measures, starting with careful personal hygiene of those involved in handling and distributing food – experts recommend – can prevent its spread.
The rules and advice to follow are typical of the prevention of any food poisoning: wash your hands very well before touching food; do not work and above all do not come into contact with food when you are unwell, especially if you are suffering from gastroenteritis, and up to three days after recovery; carefully wash and disinfect all materials and surfaces (from tablecloths and napkins to aprons and work towels, up to utensils) that may have come into contact with an infected person and/or with the virus; use only foods of certified origin, especially in the case of foods that are undercooked, such as seafood or fresh vegetables; eliminate all food supplies that may have been contaminated by an infected worker and/or other sources of norovirus; keep people wearing nappies and diapers separate, especially in nurseries and retirement homes, from areas where food is prepared and distributed.
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