Norovirus infection is an acute viral disease, manifested mainly by gastroenteritis syndrome. The main symptoms are nausea, vomiting, pain, rumbling in the stomach and liquid watery stools, less often – a pronounced temperature reaction of the body, respiratory manifestations. Diagnosis of the disease consists in the detection of the virus in biological materials, antibodies to it in the patient’s blood. Treatment is usually symptomatic, aimed at correcting the water-electrolyte balance. Enzymes, sorbents, antispasmodics are used; a sparing diet is of great importance.
A08.1 Acute gastroenteropathy caused by the pathogen Norwalk
Norovirus infection is a viral lesion of the intestine. The pathogens of the disease were first isolated in 1972 in the USA and named Norfolk viruses in honor of the place of discovery. Nosology is widespread everywhere, typical seasonality is winter time. In summer, outbreaks can occur in organized children’s groups. Noroviruses are the causes of intestinal infections in 50-90% of adult cases and 30% of school-age children. Children, people with the first blood group, pregnant women, the elderly, and HIV-infected people are considered risk groups for norovirus infection.
The causative agent of the disease is an RNA–containing human norovirus belonging to the Calicivirus family. More than 7 genetic groups of the virus are known, only three are considered pathogenic for humans. The sources of the infectious agent are patients or asymptomatic carriers, cases of virus isolation from the body within two weeks after recovery are described. The preferred route of transmission is contact when sharing household items and dishes contaminated with pathogens.
Food infection is associated with the use of thermally unprocessed food (ice cream, fresh vegetables, herbs, shellfish) prepared with unwashed hands, water – when using unboiled tap water, less often from poorly treated coolers. The virus is most easily transmitted at low temperature and high humidity. The pathogen is stable in the environment, remains viable for more than 28 days. Inactivation of norovirus is possible only with the use of chlorine-containing disinfectants.
The pathogenesis of norovirus infection has not been sufficiently studied, including due to the complexity of animal modeling. When it enters the digestive system, norovirus disrupts the motility of the stomach, shows its tropicity to the cells of the small intestine, especially the duodenum and jejunum. Viral particles can also be found in the spleen, ileum, mesentery lymph nodes, and large intestine. Replication of noroviruses leads to destruction of the intestinal epithelium, atrophy of intestinal villi, hypertrophic changes in glands, disorders of carbohydrate absorption. Local inflammatory reactions depend on the preservation of mucosal immunity, the systemic immune response and the production of specific antibodies occur no earlier than 96 hours from the moment of penetration of the pathogen into the body.
The incubation period of the disease is 4-48 hours. The clinical picture develops acutely, begins with an increase in body temperature to 38 ° C or more, chills, body aches, pain in muscles, joints, sharp weakness. A third of patients with norovirus infection notes the appearance of sore throat, runny nose, dry cough. Then there is a decrease in appetite, nausea, repeated vomiting of gastric contents. Patients complain of aching abdominal pain, mainly in the epigastrium, the umbilical region, rumbling, frequent, abundant loose stools with mucus.
An increase in thirst, hoarseness, the appearance of pulling pains, cramps in the hands, calf muscles, pronounced dryness of the skin and mucous membranes, a decrease in the amount of urine excreted, impaired consciousness are indications for an emergency doctor’s consultation. In the case of a small child’s illness, the alarming symptoms are silent tearless crying, rare urination, refusal to eat, convulsions, skin folds that do not heal within a few minutes, a large fontanel sinking.
The most common complications of norovirus infection are considered to be the consequences of dehydration of the body: hypovolemic shock, acute renal, cardiovascular insufficiency, thrombosis. Children may experience afebrile seizures, necrotic enterocolitis, bronchiolitis, ischemic colitis. Rare complications described in isolated patients are encephalopathy, hemolytic-uremic syndrome, hemophagocytic lymphohistiocytosis, DIC syndrome, benign inflammation of the liver. The long-term consequences of infection include constipation and the appearance of gastrointestinal reflux.
Manifestations similar to the clinic of this viral disease require mandatory consultation with an infectious disease specialist. Examinations by a surgeon and a pediatrician are indicated with the development of an acute abdominal clinic and the appearance of symptoms of the disease in a child, especially a younger age. Diagnostic manipulations include instrumental and laboratory research methods:
- Objective inspection. During physical examination, turgor, dryness of the skin, mucous membranes are assessed, hoarseness of the voice, the presence of convulsions are detected. Sometimes there is hyperemia of the throat, nasal congestion. Palpation of the abdomen reveals rumbling, local soreness along the course of the small intestine, negative symptoms of irritation of the peritoneum. Vomit, gastric lavage waters include only its contents. Feces on examination are watery, abundant, with a lot of mucus.
- Laboratory tests. The general blood test reveals normocytosis, lymphopenia, less often – leukocytosis. The change in the biochemical parameters of the blood occurs within the limits of a decrease in the amount of total protein, hypokalemia. In a general clinical study of urinary sediment, albuminuria, leukocyturia, erythrocyturia are determined. The coprogram indicates the presence of undigested fiber, muscle fibers, steatorrhea.
- Identification of infectious agents. The isolation of norovirus from the feces of patients occurs using PCR, laboratory solid-phase test systems for enzyme immunoassay of feces, immunochromatographic express tests are also used. Antibodies to the virus are detected in the blood using ELISA and RPH techniques, which has more retrospective significance. Bacteriological examination of feces, washing waters, and vomit is mandatory.
- Visualization methods. Chest X-ray, abdominal X-ray examination are performed according to indications to exclude pneumonia, perforation of ulcerative defects of the digestive tract. Ultrasound allows you to differentiate the symptoms of infection with the presence of effusion, pus and blood in the body cavities, cholelithiasis, ectopic pregnancy. ECG is indicated for all patients over 40 years of age, if there is an appropriate history of complaints.
Differential diagnosis is carried out with rotavirus, coronavirus, astrovirus, adenovirus gastroenteritis, campylobacteriosis, giardiasis, cholera, salmonellosis, dysentery, hepatitis A, E, escherichiosis, food toxicoinfections, travelers diarrhea. A similar clinical picture can be observed with poisoning, taking unusual dishes, diabetic coma, malabsorption syndrome, gastritic variant of myocardial infarction. It is necessary to exclude acute appendicitis, pancreatitis, mesadenitis, cholecystitis, mesenteric thrombosis, perforated gastric ulcer, duodenal ulcer, salpingoophoritis, endometritis, interrupted ectopic pregnancy, peritonitis.
Elderly people, pregnant women, young children, patients with severe dehydration and complicated course of the disease are subject to mandatory hospitalization. Isolation in hospital conditions is necessary for those living in dormitories, barracks, communal apartments. It is important to carry out daily cleaning with disinfectants in the room where a patient with a norovirus infection is located, the allocation of individual hygiene products and dishes. Nutrition plays an essential role in the course and outcome of the disease, a sparing diet is recommended with the exception of coarse fiber, marinades, dairy products, sweets, alcohol, seasonings. It is important to observe the water regime with the rejection of coffee, fruit and vegetable juices, carbonated drinks. Bed rest is observed until a stable temperature norm is reached within 2-3 days.
There is no specific etiotropic therapy, and expert reviews of attempts to introduce human immunoglobulin in severe infection are contradictory. The main direction in the treatment of the disease is rehydration therapy, carried out both with oral solutions (rehydrone, citroglucosolan, oralit) and by intravenous infusions (acesol, disol, chlosol, trisol). Enzyme (pancreatin, lipase), antispasmodic (drotaverine) drugs, sorbents (smectite, activated charcoal) are used, with indomitable vomiting – domperidone, metoclopramide. Vasoconstrictive nasal drops (oxymetazoline, xylometazoline), antiseptic solutions for rinsing the pharynx (chlorhexidine) are used locally.
Prognosis and prevention
The prognosis of uncomplicated disease is favorable, the mortality rate is about 0.001%. The majority of deaths occur in extreme age groups – preschoolers and the elderly. Up to 60% of cases of the disease proceed as mild with complete recovery within 1-3 days. The severe course in 1-5% of patients is due to a severe premorbid condition, severe immunosuppression, late treatment, and the addition of a secondary infection.
The vaccine has not been developed, but clinical trials of immunogens on animals have shown that the drug will be intranasal or combined – against rotavirus, hepatitis E and other infections. Some efficacy of prophylactic administration of bovine lactoferrin in children has been reported. It is necessary to refrain from eating food prepared with violations of sanitary standards, stored outside the refrigerator for a long time, avoid swallowing water when diving in lakes, rivers, drinking from untested sources.