CLINICAL AND EPIDEMIOLOGICAL INVESTIGATIONS OF AN OUTBREAK OF GASTROENTERITIS WITH NOROVIRUS ETIOLOGY IN PRAVETS, BULGARIA, MARCH 2016

Noroviruses, along with Sapoviruses are human pathogenic representatives of the family Caliciviridae. They are widely distributed. Their high resistance in the external environment, their great content in feces and vomit, and the very low infective dose of 10-100 virus particles, explain their high ability to cause outbreaks of gastroenteritis. The transmission of the infection takes place by fecal-oral route. Initial clinical symptoms occur after an incubation period of between 6-48 h. The first symptoms to appear are nausea and abdominal pain followed by persistent vomiting and intense nonbloody diarrhea. The reverse - transcriptase polymerase chain reaction RT-PCR is the method of choice to set the diagnosis. As an alternative method ELISA could be used in order to search for a viral antigen in material from feces or vomit. After recovery has taken place partial immunity appears for a short time - about two months. Our aim was to analyse the major epidemiological, clinical and laboratory characteristics in the hospitalized patients with norovirus gastroenteritis. The study included a group of 22 students from the Vocational School of Computer Systems and Technology in Pravets, Bulgaria, who got momentarily ill with severe gastroenteritis. They had a mean age of 16 years, in the range of 14-18 years, 17 boys (77%) and 5 girls (23%). The beginning was acute with fever (in all subjects), 12 of them (54%) had low-grade fever (temperature up to 38 degrees C) and three patients were febrile. Vomiting was observed in all patients and in 17 (77%) it was accompanied by nausea. Abdominal pain was present in 11 patients (50%). Diarrhea was present in seven patients (31%). Microbiological diagnosis included examination of a fecal sample for intestinal pathogenic bacteria and viruses, and in nine (41%) patients norovirus infection was demonstrated by PCR. The therapeutic approach included oral and parenteral rehydration, symptomatic treatment and diet. The patients analysed developed second degree of dehydration and had a very good response to the treatment. It was performed within 24-72 h after admission. This indicates that it should be initiated as soon as possible with regards to any early complains. Infections with noroviruses should always be suspected in cases of gastroenteritis with group character on the basis of data of eating common food in closed groups.