Noroviruses are single-stranded RNA viruses, belonging to the Caliciviridae family and responsible for the infectious pathogenesis of FOOD of gastroenteritis.
Background
Diagnostic observations and problems
Norovirus is a pathogen that has created many problems for the scientific community; it is cosmopolitan, proves to be extremely virulent and pathogenic (10 viral particles are sufficient), and affects the numerous communities that draw on the same source of meal distribution (school, hospital, prison, industrial, hotel, cruise ships, etc.) with great effectiveness. ); given its very small size (which until recently made it necessary to use the electron microscope) and the IMPOSSIBILITY of cultivating or isolating it, for a long time it was recognized only and exclusively through the dosing of antibodies in the blood.
Fortunately, for some years the experimentation has achieved remarkable results, improving the diagnostic potential of Norovirus gastroenteritis through the discovery of specific molecular markers to be detected on faecal samples, a technique that has helped to identify at least 5 Norovirus genogroups: GI, GII, GIII, GIV and GV differentiated respectively in about twenty clusters, of which at least 3 affect the human being.
Nevertheless, Norovirus remains the MAIN gastrointestinal virus widespread in developed countries.
Diffusion, contagion, development and symptoms of Norovirus gastroenteritis
Norovirus reaches its peak of spread in the winter period and is transmitted through contagion between people or cross-contamination of food, specifically through:
- Infected water
- Faecal-contamination or vomiting of the infected subject on surfaces and foodstuffs
- Nebulization and diffusion of the saliva drops of the infect, in the air, on surfaces and foodstuffs
Ultimately, Norovirus enters the body through the gold-pharynx and, once it has passed the gastric barrier, reaches the small intestine as the primary site of replication.
The foods responsible for Norovirus gastroenteritis are all cold and raw foods; those cooked and cold are associated with contamination by the infected food worker, while the foods that can autonomously generate Norovirus infections even without the intervention of the catering operators are: oysters, berries, vegetables and drinks; it is therefore deducible that these are products washed down with water that is not drinkable and likely to be contaminated with sewage. In the case of oysters, the ambiguous origin or inadequacy of the farming system is conceivable.
NB . Norovirus is extremely resistant, not at all sensitive to oxygen, and therefore has considerable longevity on the surfaces reached; like other viruses, Norovirus is sensitive to heat (but only at temperatures> 60 ° C) and can be easily destroyed by cooking.
The onset is frequently sudden but (except for immunosuppressed, always positive) the resolution is quite rapid; Norovirus incubation ranges from 12 to about 72 hours, while symptoms occur for around 24/48 or 60 hours in all.
Once the number of intestinal Noroviruses necessary to trigger the disease is reached, nausea and vomiting, watery diarrhea and abdominal cramps appear; the manifestation of flu symptoms such as low-grade fever, headache and muscle pain associated with fatigue and asthenia is not excluded.
Remedies for Norovirus
Prevention of gastroenteritis: from a hygienic point of view, it is possible to avoid contagion from Norovirus by applying all food safety standards (masks, clothing, self-control of health status, HACCP etc.), from the supply source (traceability and traceability) to the preparation in the laboratory (cooking or pasteurization, felling, conservation and protection from the atmosphere); work processes and self-control of personnel who, at the first symptom, must leave the work station are not excluded.
Treatment of gastroenteritis: in the case of Norovirus gastroenteritis, specific antiviral drugs or vaccines are NOT yet available, but (especially to service personnel) it is advisable to follow a diagnostic procedure consisting of:
- Microbiological tests
- Direct detection of antigen in faeces (ELISA)
- Search for viral RNA (RT-PCR or Real-time PCR).
However, there are frequent cases that require more medical attention, specifically all the elderly (who tend to be more prone to dehydration), children and especially the immunosuppressed, hypersensitive or those considered at risk.
The only useful recommendation is to maintain the state of hydration by drinking and not neglecting the salt contribution, especially of potassium (which is eliminated in large quantities with vomiting and diarrhea). The immuno-protection from Norovirus is developed during the illness, but lasts only for 8 weeks; it can be deduced that the same subject can be infected several times and also with a certain frequency during the year.
