'Evidence for waterborne origin of an extended mixed gastroenteritis outbreak in a town in Northern Greece, 2019'.

We investigated a large gastroenteritis outbreak that occurred in Northern Greece in 2019. A case was defined as anyone presenting with diarrhoea and/or vomiting from 24 January 2019 to 04 February 2019. We conducted a case-control study (CCS) using random selection of participants >16 years of age, residents of town X, who visited the health care centre between 25 and 28 January 2019. Moreover, we conducted a retrospective cohort study (CS) at the four elementary schools of the town. We collected clinical and water samples and the water supply system was inspected. In total, we recorded 638 cases (53% female; median age was 44 years (range 0-93)). Forty-eight cases and 52 controls participated in the CCS and 236 students in the CS. Both CCS and CS indicated tap water as the most likely source (OR 10, 95% CI 2.09-93.4, explaining 95.7% of cases; RR = 2.22, 95% CI 1.42-3.46, respectively). More than one pathogen was detected from stool samples of 6 of the 11 cases tested (norovirus, Campylobacter jejuni, Enterohemorrhagic E. coli (EHEC) and Enteropathogenic E. coli (EPEC)). Water samples, collected after ad-hoc chlorination, tested negative. Technical failures of the water tanks' status were identified. Our results suggested a waterborne outbreak. We recommended regular monitoring of the water supply system and immediate repair of technical failures.

A patient with respiratory toxigenic diphtheria in Greece after more than 30 years.

The introduction of treatment and systematic vaccination has significantly reduced diphtheria mortality; however, toxigenic strains continue to circulate worldwide. The emergence of an indigenous diphtheria case with fatal outcome in Greece, after 30 years, raised challenges for laboratory confirmation, clinical and public health management. Toxigenic Corynebacterium diphtheriae was isolated from an incompletely vaccinated 8-year-old boy with underlying conditions. The child passed away due to respiratory distress syndrome, before the administration of diphtheria antitoxin (DAT). All close contacts in family, school and hospital settings were investigated. Pharyngeal swabs were obtained to determine asymptomatic carriage. Chemoprophylaxis was given for 7 days to all close contacts and a booster dose to those incompletely vaccinated. Testing revealed a classmate, belonging to a subpopulation group (Roma), and incompletely vaccinated, as an asymptomatic carrier with an indistinguishable toxigenic strain (same novel multilocus sequence type, designated ST698). This case highlights the role of asymptomatic carriage, as the entry of toxigenic strains into susceptible populations can put individuals and their environment at risk. Maintenance of high-level epidemiological and microbiological surveillance, implementation of systematic vaccination in children and adults with primary and booster doses, availability of a DAT stockpile, and allowing timely administration are the cornerstone to prevent similar incidents in the future.

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.

Antiviral susceptibility profile of influenza A viruses; keep an eye on immunocompromised patients under prolonged treatment.

There was an increase in severe and fatal influenza cases in Greece during the 2011-2015 post-pandemic period. To investigate causality, we determined neuraminidase (NA) inhibitor susceptibility and resistance-conferring NA and hemagglutinin (HA) mutations in circulating influenza type A viruses during the pandemic (2009-2010) and post-pandemic periods in Greece. One hundred thirty-four influenza A(H1N1)pdm09 and 95 influenza A(H3N2) viruses submitted to the National Influenza Reference Laboratory of Southern Greece were tested for susceptibility to oseltamivir and zanamivir. Antiviral resistance was assessed by neuraminidase sequence analysis, as well as the fluorescence-based 50 % inhibitory concentration (IC50) method. Five influenza A(H1N1)pdm09 viruses (2.2 %) showed significantly reduced inhibition by oseltamivir (average IC50 300.60nM vs. 1.19nM) by Gaussian kernel density plot analysis. These viruses were isolated from immunocompromised patients and harbored the H275Y oseltamivir resistance-conferring NA substitution. All A(H1N1)pdm09 viruses were zanamivir-susceptible, and all A(H3N2) viruses were susceptible to both drugs. Oseltamivir-resistant viruses did not form a distinct cluster by phylogenetic analysis. Permissive mutations were detected in immunogenic and non immunogenic NA regions of both oseltamivir- resistant and susceptible viruses in the post-pandemic seasons. Several amino acid substitutions in the HA1 domain of the HA gene of post-pandemic viruses were identified. This study indicated low resistance to NAIs among tested influenza viruses. Antiviral resistance emerged only in immunocompromised patients under long-term oseltamivir treatment. Sequential sample testing in this vulnerable group of patients is recommended to characterise resistance or reinfection and viral evolution.

Resistant Shigella strains in refugees, August-October 2015, Greece.

Shigellosis is endemic in most developing countries and thus a known risk in refugees and internally displaced persons. In 2015, a massive influx of refugees into Greece, due to the political crisis in the Middle East, led to the development of appropriate conditions for outbreaks of communicable diseases as shigellosis. We present a cluster of 16 shigellosis cases in refugees, detected by the implementation of a syndromic notification system in one transit centre in Athens, between 20 August and 7 October 2015. Both Shigella flexneri (n = 8) and S. sonnei (n = 8) were identified, distributed in various serotypes. All tested isolates (n = 13) were multidrug resistant; seven were CTX-M-type extended-spectrum ß-lactamase producers. Our results indicate lack of a potential common source, although pulsed-field gel electrophoresis typing results revealed small clusters in isolates of the same serotype indicating possible limited person-to-person transmission without identifying secondary community cases related to the refugees. To prevent the spread of shigellosis, empirical antibiotic treatment as well as environmental hygiene measures were implemented. The detection of multi-drug resistance is important for determining the appropriate empirical antibiotic treatment for the more severe cases, while at the same time real-time typing is useful for epidemiological investigation and control measures.

Burkholderia cenocepacia bacteremia without respiratory colonization in an adult intensive care unit: epidemiological and molecular investigation of an outbreak.

BACKGROUND: To investigate an outbreak of Burkholderia cenocepacia bacteremia. Observational study and chart review in a multidisciplinary adult Intensive Care Unit (ICU) at a tertiary care hospital. METHODS: Patients' demographic variables, comorbid conditions, ICU admission diagnosis, disease severity and outcome were analyzed. In case-patients, time and possible sources of bacteremia, molecular assays, antimicrobial susceptibility and response to therapy were also recorded. RESULTS: During a 9-month period, 30 episodes of B. cenocepacia bacteremia were diagnosed in 21 patients. Median time for a positive blood culture was 9 days after admission. None of the case-patients had respiratory colonization prior to onset of bacteremia. Pathogen was susceptible to meropenem, piperacillin/tazobactam, ciprofloxacin and trimethoprim /sulphamethoxazole. Surveillance involved environmental and patient/personnel cultures. All samples were negative for B. cenocepacia. However, extensive assessment revealed lapses in infection control procedures. PFGE molecular typing showed that all isolates were indistinguishable. Prior surgery and septic shock on ICU admission were significantly more frequent among case-patients. These patients needed significantly prolonged mechanical ventilation, central venous catheterization and ICU hospitalization. All patients responded to antimicrobial therapy and the attributed mortality was zero. Complete elimination of the outbreak was achieved only after strict enforcement of infection control policies and ICU disinfection. CONCLUSION: The outbreak influenced ICU morbidity but it did not affect mortality. Although extensive environmental investigations failed to identify the source of infection, B.cenocepacia disappeared after implementation of control measures. Effective outbreak elimination cannot be limited to offending reservoir removal but needs to extend to efficient infection control practices.