Does tourism affect the long term course of COVID-19 pandemic in a country of destination? Evidence from a popular Greek island in 2020 where control measures were implemented

Greece opened its points of entry on July 1, 2020, with specific guidelines for travellers arriving by sea, air or land. The aim of this article is to examine the effect of tourism on the long term course of the Coronavirus Disease 2019 (COVID-19) pandemic during the pre-vaccination era (June to December 2020) on the popular Greek island of Crete. To achieve this, a cross-sectional serosurvey, repeated at monthly intervals, was conducted to compare the seroprevalence in Crete with seroprevalence in the mainland of Greece. Crete welcomed nearly 2,000,000 travellers during the 2020 summer season. Left-over serum samples were collected and obtained from public and private laboratories located in Greece, including the island of Crete. These samples were tested for the presence of anti-SARS-CoV-2 IgG antibodies. A total of 55,938 samples were collected, 3,785 of which originated from Crete. In Crete, the seroprevalence ranged between 0% (June 2020) and 2.58% (December 2020), while the corresponding seroprevalence in Greece was 0.19% and 10.75%, respectively. We identified 4.16 times lower seropositivity in Crete (2.58%) in comparison with the mainland of Greece (10.75%) during December 2020. Moreover, the monthly infection fatality rate (IFR) in Crete was calculated at 0.09%, compared with 0.21% in mainland Greece for December 2020. The island of Crete presented more than four times lower seroprevalence than the mainland of Greece, despite being a highly attractive tourist destination. This evidence supports the idea that tourism may not have affected the long term course of the COVID-19 pandemic in Greece. However, due to contradicting results from previous studies, further investigation is needed

Μέτρηση νανομηχανικών ιδιοτήτων μεμβρανών φωγιασίτη με την τεχνική της νανοδιείσδυσης

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Επιστήμη και Τεχνολογία Υλικών”112 σ.Το αντικείμενο της μεταπτυχιακής εργασίας αφορά στη μελέτη μηχανικών ιδιοτήτων μεμβρανών ζεόλιθου, συγκεκριμένα του φωγιασίτη (NaY), με την τεχνική της νανοδιείσδυσης. Η ανάγκη για μεγαλύτερη πρόοδο στην σύνθεση μεμβρανών έχει αποτελέσει κίνητρο και για την μελέτη των μηχανισμών πυρήνωσης και ανάπτυξης των ζεόλιθων. Η μελέτη των μηχανικών ιδιοτήτων θα οδηγήσει σε εκτίμηση της αντοχής και της αξιοπιστίας των ζεολιθικών δομών (νανοσκληρότητα και μέτρο ελαστικότητας) και θα συνδεθεί με τα δομικά τους χαρακτηριστικά. Οι ζεόλιθοι είναι υλικά τα οποία συνδυάζουν χαμηλή διηλεκτρική σταθερά με υψηλή μηχανική αντοχή λόγω του κρυσταλλικού πλέγματος. Υπάρχει επίσης πληθώρα κρυσταλλικών δομών με πόρους διαμέτρου συγκρίσιμης με τα μεγέθη πολλών αερίων. Τα χαρακτηριστικά αυτά σε συνδυασμό με την δυνατότητα ρύθμισης της εκλεκτικής ρόφησης των διαφόρων αερίων κάνουν τους ζεόλιθους υλικά από τα οποία θα μπορούσαν να κατασκευαστούν πολυκρυσταλλικές μεμβράνες για το διαχωρισμό αέριων μιγμάτων. Στην παρούσα μεταπτυχιακή εργασία μελετήθηκε μεμβράνη φωγιασίτη η οποία συντέθηκε πάνω σε πορώδη υπόστρωμα α-Al2Ο3 με επίπεδη γεωμετρία (δισκίο διαμέτρου 14mm, πάχους 2mm, μέσο μέγεθος πόρων 150-200nm και πορώδες 0,4) με την μέθοδο seeded growth. Πριν την κρυστάλλωση της μεμβράνης τοποθετούνται κατάλληλα κρύσταλλοι φωγιασίτη (NaY- Aldrich) στην επιφάνεια του υποστρώματος με την τεχνική dip-casting. Η σύνθεση της μεμβράνης έγινε στους 85 oC χρησιμοποιώντας γέλη με σύσταση 4.17Na2O / 1.0Al2O3 /5TEA (τριαιθανολαμίνη) / 1.87SiO2 / 460H2O. Η διάρκεια της σύνθεσης ήταν 120 ώρες. Η ταυτοποίηση δομής των κρυστάλλων έγινε με XRD (Bruker D-8 ADVANCE diffractometer εξοπλισμένο με LynxEye ανιχνευτή θέσης και μια CuKa πηγή ακτίνων Χ (40 kV, 40 mA)) και παρατηρήθηκε ότι ευνοήθηκε και η ανάπτυξη κρυστάλλων ζεόλιθου Α (LTA). Η μορφολογία και το μέγεθος των κρυστάλλων προσδιορίστηκαν με SEΜ (LEO-SUPRA 35VP Field Emission Scanning Electron Microscope). Στη συνέχεια πραγματοποιήθηκαν δύο σειρές μετρήσεων με την τεχνική της νανοδιείσδυσης. Κατά την πρώτη σειρά μετρήσεων πραγματοποιήθηκε φόρτιση μέχρι ένα μέγιστο φορτίο και στην συνέχεια αποφόρτιση. Από τις πειραματικές μετρήσεις μελετήθηκαν η χρονική εξέλιξη του εφαρμοζόμενου φορτίου, η συμπεριφορά του υλικού στο εφαρμοζόμενο φορτίο (καμπύλες φόρτισης-αποφόρτισης), οι νανομηχανικές ιδιότητες καθώς και το φαινόμενο Indentation Size Effect (ISE). Επίσης πραγματοποιήθηκε ανάλυση των λόγων H/Er και H3/Er2 και πλαστικότητας και στην συνέχεια μελετήθηκαν οι μηχανισμοί αποδόμησης (pile-up και sink-in) κατά τη διάρκεια της νανοδιείσδυσης. Οι τιμές που υπολογίστηκαν από τα πειραματικά δεδομένα συμφωνούν με αντίστοιχες από μελέτες της βιβλιογραφίας. Στη δεύτερη σειρά μετρήσεων, πραγματοποιήθηκε μελέτη ερπυσμού (φόρτιση για 5 s, διατήρηση σταθερού φορτίου για 35 s και αποφόρτιση για 5 s). Από τις πειραματικές μετρήσεις που προέκυψαν μελετήθηκαν η χρονική εξέλιξη του εφαρμοζόμενου φορτίου, η συμπεριφορά του υλικό στο εφαρμοζόμενο φορτίο (καμπύλες φόρτισης-αποφόρτισης), οι νανομηχανικές ιδιότητες καθώς και το φαινόμενο ISE. Επίσης πραγματοποιήθηκε ανάλυση των λόγων H/Er και H3/Er2 και στην συνέχεια οι μηχανισμοί αποδόμησης (pile-up και sink-in). Σ’ αυτή την σειρά μετρήσεων μελετήθηκε και η χρονική εξέλιξη της μετατόπισης της ακίδας και τέλος έγινε μαθηματική προσέγγιση σε κάθε μία από τις καμπύλες αυτές. Οι τιμές που υπολογίστηκαν από τα πειραματικά δεδομένα συμφωνούν με αντίστοιχες από μελέτες της βιβλιογραφίας. Τέλος, έγινε σύγκριση των αποτελεσμάτων που προέκυψαν από τη νανοδιείσδυση με και χωρίς ερπυσμό. Η σύγκριση έδειξε ότι ο ερπυσμός δεν είναι παράγοντας που επηρεάζει τα αποτελέσματα που προέκυψαν από τις δύο σειρές πειραμάτων - μετρήσεων.The subject of this master thesis is the study of mechanical properties of zeolite films, specifically faujasite membranes (NaY), by using Nanoindentation. The demand for further progress at the field of membrane composition is a motivation for extensive study at the mechanisms of calcination and growth of zeolites. The study of mechanical properties will lead to an assessment of zeolite structures strength (nanohardness and modulus) according to zeolite structural characteristics. Zeolites are materials that combine low dielectric constant with high mechanical strength owing to their crystallic structure. There are several crystallic structures with pore diameters equal to the size of many gas molecules. As zeolites combine the aforementioned features as well as the possibility of adjusting the selective sorption of various gases; they can be raw materilas for contructing polycrystalline membranes, which are used to separate gas mixtures. In this work, faujasite membranes were synthesized on the polished surface of homemade porous α-Al2O3 disks (diameter: 14mm; thickness: 2mm; mean pore size: 150-200nm and porosity: ~0.4) using the seeded growth method. Prior to hydrothermal treatment, NaY (Aldrich) crystals were deposited on the support using a dip-casting technique. The seeded supports were dried in the air and then they were placed in polypropylene bottles. The membranes were synthesized at 85oC using a gel with molar composition of 4.17Na2O / 1.0Al2O3 / 5TEA (triethanolamine) / 1.87SiO2 / 460H2O. The duration of the synthesis was 120 hrs. After hydrothermal growth, the membranes were thoroughly washed several times with hot distilled water and were then calcined in air at 420oC (heating rate 2oC.min-1) for 6 hours. Powder X-ray diffraction (XRD) patterns were obtained using a Bruker D-8 ADVANCE diffractometer equipped with a LynxEye position sensitive detector and a CuKa X-ray source (40 kV, 40 mA). Most of the reflections shown correspond to those of zeolite FAU. However there are few reflections that correspond to those of zeolite LTA. The relative intensities of the peaks of the two zeolites indicate that the film is comprised primarily by FAU type crystals. Scanning Electron Microscopy (SEM) images of the top views of the films were acquired using a LEO-SUPRA 35VP Field Emission Scanning Electron Microscope operated at 20kV in the variable pressure mode. The SEM images show the morphology and the size of crystals. Then two series of measurements were carried out using Nanoindentation. The first Nanoindentation test consists of two parts: i) loading to the maximum force and ii) unloading. During to this experiment, measurements were taken for: the time effect of the applied load to the zeolite, the material behavior (load-unload curves), the nanomechanical properties, Indentation Size Effect (ISE), the ratios H/Er, H3/Er2, and sink-in/pile-up. The results were studied and it has been concluded that they are in accordance with the ones from previous researches that were found through various bibliography sources. The second Nanoindentation test consists of three parts: i) loading to the maximum force ii) creep at maximum force and iii) unloading (5s linear load, 35s hold, and 5s linear unload). During to this experiment, measurements were taken for: the time effect of the applied load to the zeolite, the material behavior (load-unload curves), the nanomechanical properties, Indentation Size Effect (ISE), the ratios H/Er , H3/Er2, and sink-in/pile-up. Moreover, the depth of the intender in relation with the time was studied, resulting to several depth-time curves; to each of them a mathematical adjustment was made. The results were studied and it has been concluded that they are in accordance with the ones from previous researches that were found through various bibliography sources. Finally, we compared the results that obtained from the two above experiments, without creep (1st experiment) and with creep (2nd experiment). This comparison shows that the creep is not a factor that affects the results obtained by the two experiments that were performed.Μαρία Α. Κυρίτσ

Short-Term Selection to Diflubenzuron and Bacillus thuringiensis Var. Israelensis Differentially Affects the Winter Survival of Culex pipiens f. Pipiens and Culex pipiens f. Molestus (Diptera: Culicidae)

The Culex pipiens (Diptera: Culicidae) mosquito is of high medical importance as it is considered the prime vector of West Nile virus. In Europe, this species consists of two forms, named pipiens and molestus, that exhibit substantial differences in their overwintering biology. Diflubenzuron (DFB) and Bacillus thuringiensis var. israelensis (Bti) are two of the most used larvicides in mosquito control, including that of Culex pipiens. The high dependency on these two larvicides poses major concerns for resistance development. The evolution and stability of resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions, such as the winter period. This study investigated how short-term selection of pipiens and molestus forms to both larvicides affect their overwintering success. Larvae from each form were subjected to the same selective pressure (80% mortality) for three successive generations with DFB and Bti. At the end of this process, the winter survival between the selected populations and the controls (colonies without selection) was determined for each form. Selection to both larvicides significantly reduced the winter survival rates of molestus but not of pipiens form, indicating potential differences in the persistence of the selected individuals from year to year between the two forms

<i>Legionella</i> Colonization of Hotel Water Systems in Touristic Places of Greece: Association with System Characteristics and Physicochemical Parameters

This study aimed to assess the colonization of hotel water systems in central Greece and Corfu by Legionella, and to investigate the association between physicochemical parameters and Legionella colonization. Standardized hygiene inspection was conducted in 51 hotels, and 556 water samples were analyzed for Legionella spp. Free chlorine concentration, pH, hardness, conductivity, and trace metals were defined in cold water samples. The results of inspections and chemical analyses were associated with the microbiological results using univariate and logistic regression analysis. According to the score of the checklist used for the inspections, 17.6% of the hotels were classified as satisfactory, 15.7% as adequate, and 66.7% as unsatisfactory. Moreover, 74.5% of the hotels were colonized by Legionella spp. and 31.4% required remedial measures according to the European guidelines. Legionella spp. were isolated in 28% of the samples. Unsatisfactory results of inspections were associated with Legionella presence (relative risk (RR) = 7.67, p-value = 0.043). In hot-water systems, &lt;50 &#176;C temperatures increased the risk of Legionella colonization (RR = 5.36, p-value &lt; 0.001). In cold-water systems, free chlorine concentration &lt;0.375 mg/L (odds ratio (OR) = 9.76, p-value = 0.001), pH &#8805; 7.45 (OR = 4.05, p-value = 0.007), and hardness &#8805;321 mgCaCO3/L (OR = 5.63, p-value = 0.003) increased the risk, whereas copper pipes demonstrated a protective role (OR = 0.29, p-value = 0.0024). The majority of the hotels inspected were colonized with Legionella. Supplementary monitoring of the risk factors that were identified should be considered

Pilot Implementation of SARS-CoV-2 Wastewater Surveillance on Cruise Ships Arriving at the Port of Piraeus from June to November 2021

This study evaluated the usefulness and validity of wastewater SARS-CοV-2 monitoring in passenger ships. Wastewater grab samples (n = 54) were collected from seven cruise ships arriving at the port of Piraeus from June to November 2021. Samples were analyzed for the presence of SARS-CoV-2 RNA with an RT-PCR based method. Results were compared against the number of cases detected on the ships before arrival. It was demonstrated that sewage monitoring can detect the presence of SARS-CoV-2, even with few cases on board. Future efforts should focus on the collection of more representative samples to increase the consistency and validity of the investigated practice

Performance Evaluation of a Rapid Antigen Test (RAT) during Omicron Pandemic Wave in Greece, Conducted by Different Personnel, and Comparison with Performance in Previous Wave (Alpha Variant) Period

Due to the prevailing ambiguity regarding the performance of rapid antigen tests (RATs) for B.1.1.529 (Omicron) variant diagnosis, a commercial RAT was evaluated in the emergency ward of a general hospital in Larissa, Central Greece. The sampling and the evaluation were repeated twice by different personnel. Discordance between the two samplings was observed regarding the sensitivity (47.5%, 95% CI: 39.0&ndash;56.1 vs. 78.6%, 95% CI: 69.1&ndash;86.2) and specificity (93.8%, 95% CI: 86.0&ndash;97.9 vs. 100.0%, 95% CI: 93.3&ndash;100.0) of the RAT. Furthermore, the test displayed slightly lower sensitivity (78.6% vs. 85.5%, 95% CI: 79.1&ndash;90.5) compared to its initial evaluation that was conducted by our team when the B.1.1.7 (Alpha) variant was dominant

Clusters of Healthcare-Associated Legionnaires’ Disease in Two Hospitals of Central Greece

Healthcare-associated Legionnaires’ disease often leads to fatal respiratory tract infection among hospitalized patients. In this report, three cases of Legionnaires’ disease among patients in two different hospitals (Hospital A and Hospital B) were investigated. After conducting an epidemiologic and environmental investigation, the water distribution systems (WDSs) were identified as the possible source of infection, as Legionella pneumophila serogroup 1 (Lp1) was isolated from both clinical and environmental samples. Patients received aerosol therapy with nebulizers during their hospitalization. Based on the results of the investigation, the hospitals’ infection control committees reviewed their policies for Legionnaires’ disease prevention and implemented control measures focusing on using sterile fluids for aerosol treatments

Bacterial Communities and Antibiotic Resistance of Potential Pathogens Involved in Food Safety and Public Health in Fish and Water of Lake Karla, Thessaly, Greece

Bacterial communities, microbial populations, and antibiotic resistance of potential pathogens in the water and fish (Cyprinus carpio, flesh and gut) from different areas (A1, A2 and A3&mdash;A1 was linked with river water, A2 with cattle activity, and A3 with waters of a spring after heavy rains) of Lake Karla (Thessaly, Central Greece) were investigated. The isolated bacteria were identified using Matrix-assisted laser desorption ionization&ndash;time of flight mass spectrometry (MALDI-TOF MS) and were tested for resistance in 21 antibiotics. The microbiota composition of fish flesh was also studied using 16S amplicon-based sequencing Serratia fonticola and several species of Aeromonas (e.g., Aeromonas salmonicida, Aeromonas bestiarium, Aeromonas veronii, etc.) exhibited the highest abundances in all studied samples, while the microbiota profile between the three studied areas was similar, according to the culture-dependent analysis. Of them, S. fonticola was found to be resistant in the majority of the antibiotics for the water and fish (gut and flesh), mainly of the areas A1 and A2. Regarding 16S metabarcoding, the presence of Serratia and Aeromonas at genus level was confirmed, but they found at very lower abundances than those reported using the culture-dependent analysis. Finally, the TVC and the rest of the studied microbiological parameters were found at acceptable levels (4 log cfu/mL or cfu/g and 2&ndash;4 log cfu/mL or cfu/g, extremely low levels of E. coli/coliforms) in both water and fish flesh. Based on our findings, the water of Lake Karla would be used for activities such as irrigation, recreation and fishing, however, the development and implementation of a quality management tool for Lake Karla, to ensure environmental hygiene and prevention of zoonosis during the whole year, is imperative

COVID-19 Outbreak on a Passenger Ship and Assessment of Response Measures, Greece, 2020

We describe response measures to an outbreak involving 128 (33.4%) coronavirus disease cases (46.1% asymptomatic) among 383 persons onboard a passenger ship. Multivariate analysis indicated that dining in certain rooms and bar areas, nationality, working department (for crew members), and quarantining onboard the ship were significantly associated with infection

Environmental contamination of SARS-CoV-2 on surfaces, air-conditioner and ventilation systems

Background: COVID-19 can be transmitted directly through respiratory droplets or indirectly through fomites. SARS-CoV-2 has been detected on various environmental surfaces, air samples and sewage in hospital and community settings. Methods: Environmental samples were collected from a ferryboat during a COVID-19 ongoing outbreak inves-tigation and a nursing home and from three COVID-19 isolation hospital wards and a long-term care facility where asymptomatic COVID-19 cases were isolated. Samples were tested by real-time reverse transcriptase-polymerase chain reaction. Results: SARS-CoV-2 was detected on swab samples taken from surfaces of food preparation and service areas, hospital isolation wards, an air exhaust duct screen, air-conditioning filter, sewage treatment unit and air sample during investigations conducted in response to COVID-19 outbreaks on a ferryboat, nursing home, isolation facility and COVID-19 hospital wards. Discussion: Food preparation areas and utensils can be contaminated during COVID-19 outbreaks. Respiratory droplets/nuclei from infected persons can be displaced by the air flow and deposited on surfaces. It can be assumed that in the same manner, air flow could transfer and deposit infected respiratory droplets/nuclei from infected persons to the mucous membranes of persons standing against the air flow direction