Danai Pervanidou

Jingmen tick virus (JMTV) is an emerging, segmented RNA virus in the Flaviviridae family. Since its first identification in 2010 in China, JMTV has been detected in several parts of the world, primarily in ticks, but also in other arthropods, mammals, and even humans. The study included 400 adult ticks (333 Rhipicephalus bursa, 40 Ixodes ricinus and 27 Ixodes gibbosus) previously collected from livestock and the environment in various administrative regions of Greece. The ticks were grouped into 107 pools and screened for JMTV using an in-house real-time RT-PCR protocol. JMTV was detected in 41 (38.3%) tick pools (minimum infection rate 10.2%) in five of the seven regions tested. The virus positivity differed among tick species, hosts and regions. A single JMTV-positive R. bursa tick has been previously found co-infected with Aigai virus. Five positive pools with the highest viral load (Ct range 14.61–20.36) were subjected to metagenomic next-generation sequencing. Genetic analysis based on the complete coding sequences of all four RNA segments revealed that the sequences of the Greek strains cluster within JMTV Group 1, sharing 95.41% to 97.16% nucleotide identity with their closest relatives from Kosovo, Romania, and Türkiye. The results of the study confirm the wide distribution of JMTV in ticks in Greece, providing the first comprehensive genomic data for the virus in the country and highlighting the need for surveillance studies to assess any public health risk.

Background: Malaria is currently ranked as an important public health issue in Greece despite its initial eradication back in 1974. Given that the clinical picture is often nonspecific, the need for the implementation of targeted laboratory methodologies is imperative to ensure prompt Plasmodium identification and diagnosis. Methods: A total of 780 clinical samples from 763 suspected malaria cases from the National Malaria Reference Center were analyzed within a seven-year period (2017–2023). A composite laboratory reference standard methodology, including rapid diagnostic testing, microscopy, and polymerase chain reactions, was implemented for the purposes set by the current study in a group of 532 samples. A multivariable statistical analysis was implemented for the interpretation of the extracted data. Results: Microscopy and PCR successfully identified P. falciparum (111 vs. 131) and P. vivax (95 vs. 95) clinical samples. In addition, microscopy successfully identified selected cases of P. ovale (16) and P. malariae (nine), with current cases being confirmed by targeted, species-level real-time PCR protocols. Conclusions: The current study highlighted the importance of microscopic examination in malaria diagnostic procedures for Plasmodium species identification and typing. The combination of microscopy and PCR ensures a credible laboratory approach for submicroscopic clinical cases and patients with prior antimalarial treatment. This composite laboratory reference standard methodology is recommended by the Greek Malaria Reference Center for prompt identification of Plasmodium species in suspected malaria clinical cases.

Usutu virus (USUV) is a mosquito-borne flavivirus, widely distributed in Central Europe, where it causes avian outbreaks with large-scale mortality. Although most human infections are asymptomatic or mild, the reports of USUV neurologic infections are increasing, especially among immunocompromised patients. Cross-reactivity in serological and molecular assays is often seen between USUV and the genetically and antigenically related West Nile virus (WNV). Here, we report the first USUV infection in Greece in an asymptomatic blood donor who tested positive in the automated nucleic acid test during screening for WNV, which is endemic in the country. Following the blood donation surveillance plan, a serum sample taken two weeks post-donation was tested for WNV IgM and IgG antibodies. The borderline index of the IgM antibodies, combined with negative result for IgG antibodies, raised the suspicion of molecular cross-reactivity with USUV. Although the USUV-specific PCR in donor’s plasma was negative, its result was positive following amplification of the virus in cell culture, as USUV RNA was detected in the culture supernatant confirming the USUV infection. Whole genome sequence was taken using an Ion Torrent next-generation sequencing platform. Phylogenetic analysis showed that the Greek strain clusters within the USUV Europe 2A genetic lineage. The detection of USUV human infection in Greece prompts for surveillance studies to elucidate its epidemiology and ecology in the country.

Ixodid ticks are vectors for a plethora of pathogens, including the Crimean–Congo hemorrhagic fever virus (CCHFV), which causes severe disease in humans. Two autochthonous CCHF human cases were reported in 2025 in Greece. The aim of the present study was to gain a better insight into the geographic distribution and prevalence of CCHFV and the related Aigai virus (AIGV) in ticks in Greece. Therefore, 680 ticks (135 Hyalomma and 545 Rhipicephalus ticks) collected during 2024 from livestock (sheep, goats, cattle) and from the environment were tested for CCHFV and AIGV. AIGV was detected in 12 adult Rhipicephalus bursa ticks (12/511, 2.3%), while all Hyalomma ticks and R. bursa nymphs were negative for both viruses. AIGV-positive ticks were collected in May and June from goats and sheep in two distantly located regional units of Greece. AIGV sequences from partial S RNA segment differ from the prototype AIGV strain (AP-92) by 10.3% and 1.4% at the nucleotide and amino acid level, respectively. Integrated surveillance studies are needed in ticks, humans, wild and domestic animals within a One Health framework to gain a better insight into the epidemiology of CCHF in Greece, while clinical research is needed to elucidate the impact of AIGV in public health.

Background: Malaria is primarily transmitted through mosquito bites; occasionally, direct transmission through blood has been reported. Healthcare-associated infections refer to infections acquired in a hospital or another healthcare setting. Aim: This systematic review aims to explore determinants of healthcare-associated malaria (HAM) cases. Method: This review follows the PRISMA guidelines and was registered in PROSPERO (CRD42022309701). We searched five databases for publications on HAM cases published between 1 January 2000 and 7 December 2023. We initiated a data call for HAM cases to public health authorities from 37 European countries. We performed a backward and forward search, reviewed health authorities’ websites, performed searches on Google and the European Scientific Conference on Applied Infectious Disease Epidemiology (ESCAIDE) conference abstracts book. Results: We identified 37 studies on HAM comprising 55 HAM cases, of which 35 (64%) were infected in Europe, primarily in Spain (nine cases), France and Italy (seven cases each). All cases were infected with Plasmodium falciparum except one individual. Fifty HAM cases were hospital inpatients and five were healthcare workers. Five patients died. Flushing of vascular catheters with contaminated heparin/saline solution and manipulation of intravenous catheters were the most frequently reported procedures leading to infection among patients. Conclusions: While rare, HAM transmission can be fatal. Healthcare-associated malaria is preventable through strict adherence to infection prevention and control procedures. Despite extensive investigations, the procedure leading to infection often remained unknown, highlighting the complexity of investigations. Guidance and protocols for conducting investigations may improve the success rate of such inquiries.

Greece has been malaria-free since 1974, after an intense malaria control program. However, as Greece hosts migrant populations from P. vivax malaria-endemic countries, there is a risk of introducing the disease to specific vulnerable and receptive areas of the country. Knowledge of the genetic diversity of P. vivax populations is essential for understanding the dynamics of malaria disease transmission in a given region. We used nine highly polymorphic markers to genotype 124 P. vivax-infected archived DNA samples from human blood specimens referred to the NMRL from all over Greece throughout 2015–2019. The genotypic variability of the samples studied was noted, as they comprised several unique haplotypes, indicative of the importation of a large number of different P. vivax strains in the country. However, only a few events of local transmission were recorded. Genotyping revealed and confirmed the same clusters as those identified through epidemiological investigation. In only one introduction event was the index case found. No sustained/ongoing malaria transmissions in/between the studied regions or during consecutive years or additional foci of local transmission were observed. Genotyping is an important component in assisting malaria surveillance, as it provides information concerning the patterns of introduction and the effectiveness of implemented malaria control and elimination measures.

Since 2010, the West Nile virus (WNV) has been established in Greece. We describe the epidemiology of diagnosed human WNV infections in Greece with a focus on the 2022 season. During the transmission period, clinicians were sending samples from suspected cases for testing. Active laboratory-based surveillance was performed with immediate notification of diagnosed cases. We collected clinical information and interviewed patients on a timely basis to identify their place of exposure. Besides serological and molecular diagnostic methods, next-generation sequencing was also performed. In 2022, 286 cases of WNV infection were diagnosed, including 278 symptomatic cases and 184 (64%) cases with neuroinvasive disease (WNND); 33 patients died. This was the third most intense season concerning the number of WNND cases, following 2018 and 2010. Most (96%) cases were recorded in two regions, in northern and central Greece. The virus strain was a variant of previous years, clustering into the Central European subclade of WNV lineage 2. The 2022 WNV season was quite intense in Greece. The prompt diagnosis and investigation of cases are considered pivotal for the timely response, while the availability of whole genome sequences enables studies on the molecular epidemiology of the disease.

Human cases of West Nile virus (WNV) infections have been recorded in Greece since 2010, with seasonal outbreaks (summer-autumn) on an almost annual basis, caused mainly by the WNV lineage 2 strain (Nea Santa-Greece-2010). National Public Health Organization (NPHO) in Greece is annually implementing enhanced surveillance of human WNV infection, in order to promptly identify human cases of WNV infection and monitor distribution in terms of time and place. Entomological surveillance activities were carried out on a national basis in 2019 and 2020, under NPHO coordination and the collaboration of several private subcontractors, along with the Unit of Medical Entomology, Laboratory for Surveillance of Infectious Diseases (LSID). The aim was to monitor mosquito species composition, abundance, and WNV circulation in mosquito pools of Culex pipiens s.l. species. Adult mosquito traps were placed in selected sites; collected samples were morphologically characterized and pooled by date of collection, location, and species types. Female Culex pipiens s.l. pools were tested for WNV and WNV infection rates (MIR and MLE) were estimated. Highest mean number of female Culex pipiens s.l. species was recorded in Central Macedonia both for 2019 and 2020. Six hundred and fifty-nine mosquito pools (147 in 2019 and 512 in 2020) of female Culex pipiens s.l. were examined for WNV presence. The highest MLE was detected in Western Macedonia in 2019 and in Thessaly in 2020. Here, we present data on the mosquito species composition in the studied areas and WNV detection in mosquitoes from areas in Greece where the specific national mosquito surveillance program was implemented, for two years, 2019 and 2020.

Background: Human cases of West Nile virus (WNV) infection are recorded since 2010 in Greece, with seasonal outbreaks occurring almost annually. Enhanced surveillance has been implemented since 2010, to promptly characterise cases’ temporal and geographical distribution and inform authorities for implementation of appropriate measures (mosquito control, health education, blood safety). Aim: We describe the epidemiology of WNV human infections in Greece focusing on the 2018 season. Methods: The National Public Health Organization advised physicians to test all suspect WNV infection cases and refer samples to reference laboratories. Laboratories notified diagnosed cases on a daily basis. Treating physicians, patients, and infected blood donors were interviewed within 48 hours after diagnosis and the probable infection location was identified. Hospitalised cases were followed up until discharge. Results: A total of 317 autochthonous WNV infection cases were diagnosed in 2018. Among them, 243 cases had neuroinvasive disease (WNND), representing a 23% increase of WNND cases compared with 2010, the previous most intense season. There were 51 deaths. Cases started occurring from week 22, earlier than usual. Both rural and urban areas were affected, with 86 (26% of the total) municipalities belonging to seven (54% of the total) regions recording cases. Two major epicentres were identified in Attica and Central Macedonia regions. Conclusions: The largest number of human cases of WNV infection ever recorded in Greece occurred in 2018, with a wide geographical distribution, suggesting intense virus circulation. Enhanced surveillance is vital for the early detection of human cases and the prompt implementation of response measures.

This report describes a cluster of SARS-CoV-2 infections in pilgrims returning from Israel to Greece. Out of 53 pilgrims, 48 (90.5%) were tested positive for SARS-CoV-2; of them, 41 (85.4%) developed symptoms consistent with COVID-19, and 7 (14.6%) remained asymptomatic. These cases suggest a high risk of COVID-19 infection for pilgrims traveling during the pandemic. Although at that time the prevalence of the disease was low in the origin and destination countries, crowded exposure to other pilgrims from many other countries led to this cluster. Increasing awareness about the risks in pilgrims is important and particularly for elderly pilgrims and those with underlying conditions.