Norovirus waterborne outbreak in Chalkidiki, Greece, 2015: detection of GI.P2_GI.2 and GII.P16_GII.13 unusual strains.

Noroviruses, along with rotaviruses, are among the leading causes of gastroenteritis worldwide and novel strains are periodically emerging. In August 2015, an unusual increase of gastroenteritis cases occurred in a touristic district in Kassandra peninsula, Chalkidiki, Northern Greece. Seven stool specimens from cases were tested positive for norovirus. Molecular investigation and phylogenetic analysis identified that there was co-circulation of norovirus GI.P2_GI.2 and the recombinant strain GII.P16_GII.13. A 1:1 case-control study conducted and showed that tap water consumption significantly associated with developing symptoms of gastroenteritis (odds ratio = 36.9, P = 0.018). The results of the epidemiological investigation, the co-circulation of two different norovirus strains, the information of a pipeline breakage at the water supply system before the onset of cases, and reports on flooded wells and sewage overflow, indicated the possibility of water contamination by sewage during the pipeline breakage leading to a large outbreak with a peak at 10 August and a possible secondary person-to-person transmission after the 16th of August. Norovirus GI.P2_GI.2 strains are rarely reported in Europe, while it is the first time that infection from the recombinant strain GII.P16_GII.13 is recorded in Greece.

A large waterborne gastroenteritis outbreak in central Greece, March 2012: challenges for the investigation and management.

In March 2012, there was an unusual increase of gastroenteritis cases in a district with 37,264 inhabitants in central Greece. It was estimated that more than 3600 people developed symptoms. A 1:1 case-control study showed that consumption of tap water was a risk factor for acquiring infection [odds ratio (OR) 2.18, 95% confidence interval (CI) 1.11-4.28]. Descriptive data, low gastroenteritis incidence in adjacent areas with different water supply systems, and water-quality data further supported the hypothesis of a waterborne outbreak. Thirty-eight stool samples were positive for rotavirus. Bacterial indicators of recent faecal contamination were detected in samples from the water source and ice cubes from a local production enterprise. Molecular epidemiology of rotavirus strains, apart from the common strain, G3[P8], identified the unusual G/P combination G2P[8]. Water sanitation measures contributed to the control of the outbreak. This outbreak demonstrated the need for the cooperation of laboratories with different expertise and the importance of early notification of waterborne gastroenteritis outbreaks.

Management and investigation of viral gastroenteritis nosocomial outbreaks: lessons learned from a recent outbreak, Greece, 2012.

BACKGROUND: A nosocomial outbreak in a 740-bed hospital in Athens, Greece, was investigated in January-February 2012. METHODS: Recommendations on infection control measures were given and two case-control studies were conducted among patients (study A) and health care workers (HCWs) (study B). Compliance to control measures was evaluated. RESULTS: The absence of a routine recording system of nosocomial-acquired gastroenteritis cases led to a 10 days delay in outbreak identification. In total, 63 gastroenteritis cases were identified; 30 HCWs and 33 patients. In the multivariable analysis of study A the disease incidence among patients was statistical significantly associated with a prior incident of vomitus in their room (OR=7.96, 95% CI=1.29-49.2). In study B, the incidence was associated with the history of direct contact with a symptomatic patient (OR=3.03, 95%CI 1.01-9.12). Twenty one (75%) of the symptomatic HCWs reported absence from work for a median of 2 days (range: 1-4). Seven (25.0%) continued to work despite being symptomatic. Only, 11.1% of patients were isolated or cohorted after developing symptoms. In-hospital virological testing was not feasible and one specimen sent to a university laboratory was positive for norovirus. CONCLUSIONS: An appropriately designed protocol regarding the detection, the management and the laboratory investigation of nosocomial gastroenteritis outbreaks should be followed in order effective containment to be reassured. Hippokratia 2014; 18 (3): 204-208.