Giulietta Venturi

West Nile virus (WNV) is a flavivirus whose cycle involves mosquitoes and avian hosts that occasionally may infect horses and humans as “dead‐end hosts.” Human infection is mostly asymptomatic, sometimes leading to febrile or neuroinvasive disease. In 2025, Italy experienced its largest epidemic with an unprecedented geographic spread (79 provinces; 52% of cases in central Italy). Here we report whole‑genome sequencing and phylogeographic analysis of 39 WNV lineage 2 samples collected in Lazio and Campania regions between July and September 2025 from humans and animal samples. All 2025 strains belonged to a Southern Italian clade that diversified around 2020, with evidence of earlier circulation in 2024. All the 2025 genomes shared a substitution that lies in envelope protein domain III (K399R), potentially influencing interactions with the viral membrane. The same mutation was previously detected in Eastern European strains, leading to the hypothesis of introductions in Italy via migratory birds from these regions. Phylogeography identified strong viral dispersal routes within Central Italy supporting a pattern of short‑range spread and local overwintering. Overall, results highlight the roles of ecological conditions and cross‑border transmission dynamics in shaping the 2025 Italian epidemic, underscoring the need for integrated genomic/ecological surveillance.

Background: Phlebotomine sand-fly-borne infections are an emerging threat to human and animal health in Mediterranean countries, highlighting the need for improved surveillance and control strategies. Dogs are ideal sentinel hosts owing to their central role in the transmission of zoonotic Leishmania infantum , frequent exposure to sand fly bites, capacity to develop antibodies to phleboviruses, and close contact with humans. This study reports cross-sectional surveys of antibodies to Leishmania , Toscana virus (TOSV), and Sicilian sand fly virus (SFSV) in dogs from Portugal, Spain, Italy, Croatian Istria, Turkey, and Israel, as well as antibodies to salivary proteins of Phlebotomus perniciosus (Portugal, Spain, and Italy) and Phlebotomus papatasi (Spain and Italy), conducted within the Climate Monitoring and Decision Support Framework for the Detection and Mitigation of Sand fly Diseases with Cost–Benefit and Climate Policy Measures (CLIMOS) project. Methods: Blood samples and epidemiological data were collected from 2500 dogs. Antibodies to Leishmania were detected by indirect immunofluorescence, phlebovirus antibodies by seroneutralization assays, and antibodies to P. perniciosus and P. papatasi salivary antigens by enzyme-linked immunosorbent assay (ELISA) using recombinant proteins rSP03B and rSP36, respectively. Sources of antibody variability were evaluated using mixed-effects logistic regression models. Results: Antibodies to L. infantum , phleboviruses, and sand fly saliva were widely detected, although seroprevalence varied markedly by region. No Leishmania -seropositive dogs were found in Istria, parts of northern Spain, or several districts in Israel, whereas seroprevalence exceeded 30% in Sicily and in several Turkish and Spanish provinces. TOSV seropositivity was generally absent or below 5%, except in southern Spain (8–24%) and Muğla, Turkey (10%). SFSV exposure was highly focal, occurring mainly in Turkey (12%), Israel (12%), and Lisbon (7%). Exposure to P. perniciosus was very high in Portugal, Sicily, and most of Spain, while P. papatasi exposure was highest in Sicily and selected Spanish regions. Antibody variability was driven primarily by geographical location. Conclusions: The marked geographical heterogeneity observed confirms dogs as valuable sentinels for sand-fly-borne infections. These infections are highly clustered across Mediterranean regions, likely reflecting differences in sand fly density and infection rates. Understanding the drivers of this heterogeneity is essential for accurate risk mapping and effective control strategies.

Dengue remains one of the most significant tropical diseases, with its geographic range continuing to expand. The etiological agent of the disease is dengue virus, a term that groups four closely related viruses defined as serotypes. The four dengue virus serotypes elicit distinct serological responses, and their replacement or co-circulation in endemic regions can result in major outbreaks. The identification of the circulating serotypes is essential for surveillance and clinical management. Here we describe a novel method for the detection and serotyping of the four dengue virus serotypes using a single plex multicolor real-time RT-qPCR. The method takes advantage of a highly informative dataset that includes a realistic representation of globally circulating strains, allowing the selection of a universal primer pair and four serotype-specific hydrolysis probes. The method has been extensively tested and the results support its use in surveillance studies as well as in clinical settings.

West Nile virus (WNV) and Usutu virus (USUV) are endemic in Italy. Some regions experience high annual circulation, while others report only sporadic or low-level activity. A national survey was conducted to assess WNV and USUV seroprevalence among blood and organ donors. Between February 2021 and February 2022, serum samples were collected from 9,073 donors (8,829 blood donors and 244 organ donors) across almost all Italian regions. Samples were screened using a WNV ELISA IgG test, with positive results confirmed via plaque reduction neutralization test (PRNT) for WNV and USUV. Of the total samples, 195 (190 blood donors and 5 organ donors) tested positive by ELISA. Among these, 23 samples (20 blood donors and 3 organ donors) were confirmed WNV-positive, and 42 (41 blood donors and 1 organ donor) were USUV-positive by PRNT. Additionally, 39 donors had antibodies to both viruses. Unadjusted national seroprevalence among blood donors was 0.66% (95% CI: 0.50-0.85%) for WNV and 0.90% (95% CI: 0.71-1.11%) for USUV. Among organ donors, WNV seroprevalence was 1.64% (95% CI: 0.45-4.14%) and 0.82% (95% CI: 0.10-2.93%) for USUV. After adjustment by general population weights, national seroprevalence in blood donors was 0.90% for WNV and 1.16% for USUV. Seroprevalence was higher in historically endemic northern regions, aligning with known circulation patterns. Blood and organ donors showed similar exposure levels. These findings confirm sustained WNV and USUV presence in Italy and support the continued need for preventive safety measures in the management of Substances of Human Origin (SoHO).

CHIKV infection is transmitted by Aedes mosquitoes spp., with Ae. aegypti considered as the primary vector and Ae. Albopictus playing an important role in sustaining outbreaks in Europe. The ECSA-Indian Ocean Lineage (IOL) strain emerged in Reunion, subsequently spreading to areas such as India, the Indian Ocean, and Southeast Asia, also causing outbreaks in naive countries, including more temperate regions, which originated from infected travelers. In Italy, two authocthounous outbreaks occurred in 2007 (Emilia Romagna region) and 2017 (Lazio and Calabria regions), caused by two different ECSA-IOL strains. The phylogenetics, evolution, and phylogeography of ECSA-IOL-CHIKV strains causing the 2007 and 2017 outbreaks in Italy were investigated. The mean evolutionary rate and time-scaled phylogeny were performed through BEAST. Specific adaptive vector mutations or key signature substitutions were also investigated. The estimated mean value of the CHIKV E1 evolutionary rate was 1.313 × 10⁻³ substitution/site/year (95% HPD: 8.709 × 10⁻⁴–1.827 × 10⁻³). The 2017 CHIKV Italian sequences of the outbreak in Lazio and of the secondary outbreak in Calabria were located inside a sub-clade dating back to 2015 (95% HPD: 2014–2015), showing an origin in India. Continued genomic surveillance combined with phylogeographic analysis could be useful in public health, as a starting point for future risk assessment models and early warning.

Between August and 28 October 2024, 199 autochthonous cases of dengue virus serotype 2 were notified in the city of Fano, central Italy. We describe the ongoing epidemiological and microbiological investigation and public health measures implemented to contain the outbreak. The high transmissibility and the extension of the outbreak suggest that dengue should be expected in temperate regions during favourable seasons, highlighting the need for heightened awareness among healthcare providers and the public to ensure timely detection and response.

Arboviruses are pathogens transmitted mainly by mosquitoes, ticks, and sandflies

Aims: To evaluate whether antibodies specific for the vaccinia virus (VV) are still detectable after at least 45 years from immunization. To confirm that VV-specific antibodies are endowed with the capacity to neutralize Mpox virus (MPXV) in vitro. To test a possible role of polyclonal non-specific activation in the maintenance of immunologic memory. Methods: Sera were collected from the following groups: smallpox-vaccinated individuals with or without latent tuberculosis infection (LTBI), unvaccinated donors, and convalescent individuals after MPXV infection. Supernatant of VV- or MPXV-infected Vero cells were inactivated and used as antigens in ELISA or in Western blot (WB) analyses. An MPXV plaque reduction neutralization test (PRNT) was optimized and performed on study samples. VV- and PPD-specific memory T cells were measured by flow cytometry. Results: None of the smallpox unvaccinated donors tested positive in ELISA or WB analysis and their sera were unable to neutralize MPXV in vitro. Sera from all the individuals convalescing from an MPXV infection tested positive for anti-VV or MPXV IgG with high titers and showed MPXV in vitro neutralization capacity. Sera from most of the vaccinated individuals showed IgG anti-VV and anti-MPXV at high titers. WB analyses showed that positive sera from vaccinated or convalescent individuals recognized both VV and MPXV antigens. Higher VV-specific IgG titer and specific T cells were observed in LTBI individuals. Conclusions: ELISA and WB performed using supernatant of VV- or MPXV-infected cells are suitable to identify individuals vaccinated against smallpox at more than 45 years from immunization and individuals convalescing from a recent MPXV infection. ELISA and WB results show a good correlation with PRNT. Data confirm that a smallpox vaccination induces a long-lasting memory in terms of specific IgG and that antibodies raised against VV may neutralize MPXV in vitro. Finally, higher titers of VV-specific antibodies and higher frequency of VV-specific memory T cells in LTBI individuals suggest a role of polyclonal non-specific activation in the maintenance of immunologic memory.

The frequency of locally transmitted dengue virus (DENV) infections has increased in Europe in recent years, facilitated by the invasive mosquito species Aedes albopictus, which is well established in a large area of Europe. In Italy, the first indigenous dengue outbreak was reported in August 2020 with 11 locally acquired cases in the Veneto region (northeast Italy), caused by a DENV-1 viral strain closely related to a previously described strain circulating in Singapore and China. In this study, we evaluated the vector competence of two Italian populations of Ae. albopictus compared to an Ae. aegypti lab colony. We performed experimental infections using a DENV-1 strain that is phylogenetically close to the strain responsible for the 2020 Italian autochthonous outbreak. Our results showed that local Ae. albopictus is susceptible to infection and is able to transmit the virus, confirming the relevant risk of possible outbreaks starting from an imported case.

West Nile virus (WNV) is a public health concern in Europe. Rising temperatures and the migration of potential vectors promote the spread of viruses to previously unaffected areas. In 2023, the Apulia region of Southern Italy experienced an unexpected increase in West Nile neuroinvasive disease (WNND); no such cases had been reported in the previous 10 years. Overall, eight autochthonous cases of WNV infection were identified between July and October 2023, six of which were WNND. All cases were male (median age, 73 years). Two of the cases were blood donors. All WNND cases were hospitalized and all recovered within a few weeks. Surveillance data showed that, in the Apulia region, WNV Lineage 2 was detected in humans, mosquitoes, and horses. Based on the number of WNND cases reported, we can assume that a high number of infections occurred during the summer period. Changes in the climate in the region over recent years could be considered among the main drivers of the rapid increase in WNV infections. Therefore, integrated surveillance should be strengthened to avoid the potential massive spread of WNV in Southern Italy. Moreover, the implementation of whole-genome sequencing of WNV strains, as well as seroepidemiological studies in the area, will facilitate a better understanding of circulation dynamics.