Susceptibility of wild and domestic #songbirds to #Usutu virus

Abstract

Usutu virus (USUV) is an emerging mosquito-borne orthoflavivirus that can cause neuroinvasive disease in humans and wild birds. USUV clusters phylogenetically within the Japanese encephalitis virus serocomplex, sharing antigenic and ecological similarity with West Nile virus (WNV). USUV is maintained in an enzootic cycle primarily involving passerine birds and Culex spp. mosquitoes. USUV was first isolated in South Africa in 1959 and has since spread throughout Africa and Europe, causing mortality and disease in several wild bird populations, specifically the Eurasian blackbird (Turdus merula). To understand transmission and pathogenesis of USUV in birds, we sought to develop passerine bird models of infection using wild-caught house finches (Haemorhous mexicanus), wild-caught American robins (Turdus migratorius), domestic canaries (Serinus canaria domestica), and captive-bred zebra finches (Taeniopygia guttata). Birds were inoculated with one or two isolates of USUV and viremia was measured. House finches, American robins, and canaries were susceptible to USUV, with 100% of inoculated birds developing viremia. These avian species reach viremias that have the potential to infect Cx. quinquefasciatus mosquitoes. Clinical disease and histopathological evidence of disease were severe in American robins and moderate to severe in canaries, with limited disease in house finches. However, zebra finches inoculated with one isolate of USUV did not develop detectable viremia. These findings provide additional tools for studying USUV enzootic transmission and pathogenesis in passerine birds.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014213

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#Chikungunya fever: #Brazil is intensifying its response to address health emergency in Dourados (MoH, April 4 '26)

 

{Edited}

The Brazilian government has intensified its response to the emergency situation in Dourados (MS), given the increase in cases of chikungunya, with the mobilization of an interministerial task force that integrates actions in health, assistance, civil defense, and logistical support in the territory. The emergency affects the population of the municipality, with a greater impact on indigenous communities.

As a reinforcement to the response already underway, the Federal Government has guaranteed more than R$ 3.1 million in emergency resources for the municipality. 

Of this total, R$ 1.3 million , authorized by the Ministry of Integration and Regional Development (MIDR) in a decree published this Thursday (2), will be allocated to relief and humanitarian assistance actions, such as direct support to the population and local response structures. 

Also this Thursday, the National Secretariat for Civil Protection and Defense approved a work plan worth R$ 974,100 for restoration actions, including urban cleaning, waste removal and disposal in a licensed sanitary landfill, with resources to be transferred directly to the municipality.

The Ministry of Health has already transferred R$ 855,300 to the municipality to cover the costs of surveillance, assistance, and control actions related to chikungunya in the region.

The federal response has been underway since mid-March, coordinated by the Ministry of Health, which mobilized the National Health System (SUS) Task Force , reinforced healthcare teams, and intensified vector surveillance and control actions across the territory. 

The operation includes actively searching for cases, conducting home visits, eliminating [mosquitoes] breeding sites, and expanding services to the population, with special attention to the most vulnerable areas, including indigenous territories.

The National Health System Task Force has 40 mobilized professionals , with 26 currently working directly, and has already carried out 1,288 clinical consultations , 81 transfers for medium and high complexity care, and 225 home visits . 

The teams operate both in indigenous territories and in the municipalities of Dourados and Itaporã, supporting local management, together with the Mato Grosso do Sul State Health Secretariat, reorganizing care flows, expanding active case finding, and guaranteeing assistance, health education, and psychosocial care.

Fiocruz mobilized the shipment of pain medication, reinforcing its ability to meet local demand due to the epidemic.

To expand response capacity, the Ministry of Health authorized the emergency hiring of 50 Endemic Disease Control Agents (ACEs). Of these, 20 have already been trained and will enter the field this Friday (3), while another 30 will begin training to work from Monday (6).

In the field of vector control, actions were intensified with the mobilization of approximately 95 professionals , including Community Health Agents and Indigenous Sanitation Agents (AISAN). Between March 9 and 16, 4,319 properties were inspected , of which 2,173 received treatment , identifying 1,004 breeding sites of the Aedes aegypti mosquito , mainly in water storage containers, solid waste, and tires.

Actions were also taken to control the spread of insecticide using ultra-low volume (ULV) methods, including three cycles of vehicle-mounted ULV application and backpack spraying in 43 high-traffic areas, such as schools and health units. The volunteer effort to remove breeding sites mobilized approximately 100 people and resulted in the collection of four dump truckloads of waste.

Vector control will be reinforced with support from the Ministry of Defense. Currently, 40 Brazilian Army soldiers and five vehicles are already in the area , expanding the operational capacity of the mosquito control efforts.

The Ministry of Health also sent 1,000 Larvicide Dissemination Stations (LDSs). Of the first 300 units, 150 have already been installed in priority neighborhoods, with expansion planned for other regions of the municipality.

Through Funai (National Indian Foundation), actions are also underway to provide direct support to indigenous communities in Dourados, focusing on food security and access to water. 

The distribution of 6,000 food baskets is planned , in three stages between April and June, in coordination with the Ministry of Social Development (MDS), the National Supply Company (Conab), the Special Secretariat for Indigenous Health (Sesai), and Civil Defense. The expansion of the water supply system in the Jaguapiru and Bororó villages has also been authorized to guarantee access to potable water and improve the sanitary conditions of the indigenous communities.

Epidemiological scenario

The most recent epidemiological surveillance data, referring to April 2nd, indicates that the region has registered 2,812 notifications of chikungunya, with 1,198 confirmed, 430 discarded, and 1,184 still under investigation. The highest concentration of cases is in indigenous villages, where 822 cases were confirmed—68.6% of the total confirmations in the region. 

So far, five deaths have been confirmed in Dourados, all among the indigenous population of the municipality.

To strengthen the coordination of actions, the Ministry of Health established a Situation Room in Brasília on March 25th, with permanent meetings to monitor the situation and integrate decisions between technical teams and managers.

Within the indigenous territory, the work is carried out in a coordinated manner between the Ministries of Health, Indigenous Peoples, Integration and Regional Development, Defense, Social Development, Funai (National Indian Foundation), and the Special Indigenous Health District of Mato Grosso do Sul (DSEI-MS), which has 210 Indigenous Health Agents (AIS) and 150 Indigenous Sanitation Agents (Aisan), in addition to logistical support with 91 pickup trucks, 6 vans, and 1 truck.

The actions also include training for health professionals in the municipal and indigenous networks, aligning clinical protocols for diagnosis and proper management of the disease, as well as health education activities in schools and communities. There are also plans to send prevention messages via WhatsApp to more than 234,000 residents , in Portuguese and with translation into indigenous languages.

The response also includes improving the quality of care, with the implementation of the national chikungunya protocol and training of teams for early identification of severe cases and appropriate clinical management.

Source: 

Link: https://www.gov.br/saude/pt-br/assuntos/noticias/2026/abril/governo-do-brasil-intensifica-resposta-integrada-e-mobiliza-forca-tarefa-para-enfrentar-emergencia-sanitaria-em-dourados-ms-2

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#Culicoides (Diptera: Ceratopogonidae) in Extra-Amazonian #Oropouche #Outbreak Areas of Minas Gerais, #Brazil: #Ecological Insights into Virus Transmission

 

Abstract

Oropouche fever (OF), caused by Oropouche virus (OROV), has expanded beyond its Amazonian range into Minas Gerais (MG), Brazil, raising concern about transmission in extra-Amazonian Atlantic Forest landscapes. Critical gaps persist regarding Culicoides vector communities, anthropophily, and climate-sensitive transmission risk in these newly affected regions. We conducted targeted entomological surveys outbreak-driven by human OF cases, standardized across five MG communities using CDC light traps and Protected Human Attraction (PHA) to characterize Culicoides composition. Females of Culicoides underwent RT-qPCR for OROV (n = 819) and physiological assessment (n = 312). We developed an entomological alert framework that integrates blood-fed abundance, minimum infection rate (MIR) upper confidence bounds, and environmental drivers (i.e., mean temperature, relative humidity and precipitation) via generalized additive mixed models, which explained 68% of the variability in Culicoides abundance and the alert index across communities. We collected 1171 Culicoides individuals representing five species (C. leopoldoi, C. paraensis, C. pusillus, C. foxi, and C. limai). C. leopoldoi (79.1%) and C. paraensis (20.3%) were the predominant species; notably, C. paraensis is recognized as the primary vector of OROV in the Americas. C. paraensis was documented for the first time in all five outbreak areas and dominated PHA captures (90%), suggesting anthropophily. Although no specimens tested OROV-positive (consistent with expected field infection rates of 0.01–1%), MIR upper bounds reached 132/1000 in low-sample settings and humidity and temperature strongly modulated abundance. This operational baseline and alert index transform virologically negative, sparse surveillance data into prioritized targets for intensified sampling and vector control during early, low-prevalence phases, when containment of OROV’s extra-Amazonian spread is still achievable.

Source: 

Link: https://www.mdpi.com/1999-4915/18/3/361

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Association of avian #biodiversity and #WNV circulation in #Culex mosquitoes in Emilia-Romagna, #Italy

 

Abstract

Background

West Nile Virus (WNV) is a zoonotic arbovirus maintained in a transmission cycle between Culex mosquitoes and birds, occasionally spilling over into humans. The impact of avian biodiversity on WNV circulation remains debated, with studies reporting both negative and positive correlations (dilution and amplification effects respectively) across different settings. In Europe, this relationship remains largely unexplored, particularly in regions with high WNV transmission, such as Emilia-Romagna in Northern Italy.

Methods

We explored the association between avian biodiversity and WNV circulation in Culex mosquitoes in Emilia-Romagna using 11 years (2013–2023) of entomological surveillance data paired with two avian data sources. We calculated avian biodiversity indices (Shannon’s, Simpson’s, and Chao2) from observation records from the Farmland Bird Index project and applied linear regression models to assess their relationship with WNV detection frequency. Moreover, we used Bayesian spatiotemporal regression models and gridded weekly avian abundance estimates from the eBird project to analyse the associations between avian species richness indices and WNV transmission risk quantified by vector index (VI) at 68 geolocated mosquito traps across the region.

Results

We observed consistent negative associations between WNV detection frequency in the Culex population and avian biodiversity indices, supporting the dilution effect hypothesis (DEH). We found that non-passerine species richness was negatively associated with VI while passerine species richness showed a positive association after adjusting for covariates and spatial random effects. These findings suggest that passerines may amplify WNV transmission, whereas the presence of non-passerine species is associated with reductions in WNV circulation.

Significance

This study provides the first empirical evidence supporting the DEH for WNV in Europe. These findings have important implications for biodiversity conservation and integrated public health surveillance activities across Europe.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014076

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Serological and viral #prevalence of #Oropouche virus (OROV): A systematic review and meta-analysis from 2000–24 including #human, #animal, and #vector #surveillance studies

 

Abstract

Background

Oropouche virus (OROV) is an emerging arbovirus primarily transmitted by biting midges and is increasingly recognized as a public health threat in Central and South America. With over 11,000 confirmed cases reported in 2024, a ten-fold increase from the previous year, its transmission dynamics and true burden remain poorly understood due to diagnostic challenges and fragmented surveillance systems.

Objective

This systematic review and meta-analysis (SRMA) synthesizes OROV prevalence data in humans and summarizes the available data for vectors and animal hosts sampled between 2000 and 2024 to provide updated estimates and identify key surveillance gaps.

Methods

We systematically searched Web of Science, PubMed, Embase, Medline, and LILACS for OROV seroprevalence and viral prevalence studies in human, insect, and animal populations, published up to September 12, 2024. The review protocol was registered with PROSPERO (CRD42024551000). Studies were extracted in duplicate, and data were meta-analyzed using generalized linear mixed-effects models. Risk of bias was appraised using a modified Joanna Briggs Institute checklist.

Results

We included 71 articles reporting serological or viral prevalence of OROV across nine countries. Between 2000–2024, pooled human seroprevalence among individuals with febrile illness or suspected of Oropouche infection was 12.6% [95% CI 5.3-26.9%] across four South American countries and seroprevalence of 1.1% [95% CI 0.5-2.3%] was observed in asymptomatic groups. Viral prevalence among individuals with febrile illness or suspected of Oropouche infection was 1.5% [0.8-3.0%] across seven South American countries and Haiti. Most studies used convenience sampling and RT-PCR or hemagglutination assays. In vector populations, positive OROV prevalence in Aedes aegypti and Culex quinquefasciatus was reported in two of 18 sources, while 10.0% and 7.5% animal host prevalence was reported in dogs and cattle, respectively. We found high risk of bias in 11.3% of studies in our critical appraisal, with most animal, human, and vector studies falling in the moderate risk of bias range.

Conclusions

Despite rising numbers of OROV reported cases, prevalence estimates remain limited by sparse surveillance and variable methodology. This review highlights the urgent need for standardized serological assays, community-based studies, and expanded surveillance in animal and vector reservoirs. A One Health approach is essential to monitor OROV transmission and inform regional preparedness efforts.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013340

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Rapid #risk #assessment, acute event of potential public health concern: #Chikungunya virus disease, #Global (#WHO, Dec. 29 '25, summary)

 

Overall Risk statement

-- This RRA aims to assess the overall public health risk at the global level posed by the chikungunya virus (CHIKV) transmission during 2025, considering the criteria of potential risk for human health, the risk of geographical spread, and the risk of insufficient control capacities with available resources, and the implications for the 2026 transmission season. 

-- Chikungunya virus (CHIKV) poses a significant and growing global health risk due to large and widespread regional outbreaks in recent years, climate-driven mosquito expansion, lack of specific treatment, and increasing international travel. 

-- While mortality remains relatively low, the CHIKV infection can cause prolonged arthritis with disability as well as  severe illness in some patients. 

-- From 1 January to 10 December 2025, 502 264 CHIKV disease cases including  208 335 confirmed cases, and 186 CHIKV deaths, were reported globally. 

-- While certain WHO Regions are reporting lower case numbers compared to 2024, others are experiencing marked increases, furthermore some countries are seeing an emergence of chikungunya in previously unaffected populations. 

-- This heterogeneity in regional trends complicates the interpretation of the global situation. 

-- The data suggest localized resurgence or emergence in specific geographic areas. 

-- The region of the Americas has reported the highest number of confirmed cases followed by the European region (comprised of cases reported predominantly from French Overseas Departments in the Indian Ocean). 

-- Further, the potential for geographic spread remains substantial given that chikungunya can be introduced into new areas by infected travellers where local transmission may be established in the presence of competent Aedes mosquito, a susceptible population and favorable climatic and ecological conditions.  

-- The global public health risk posed by CHIKV transmission is assessed as moderate, driven by widespread outbreaks across multiple WHO regions during the 2025 season including areas with previously low or no transmission. 

-- The resurgence and emergence of cases in new geographic areas are facilitated by the presence of competent Aedes mosquito vectors, limited population immunity, favorable environmental conditions, and increased human mobility. 

-- The uneven distribution of cases complicates global interpretation, but highlights significant localized transmission. 

-- Control capacities remain challenged by gaps in surveillance, diagnostic access, healthcare infrastructure, and sustainable vector surveillance and control.  

-- Given the ongoing outbreaks reported globally in 2025, the potential for further spread in 2026 cannot be ruled out. 

(...)

Source: 

Link: https://www.who.int/publications/m/item/who-rapid-risk-assessment---chikungunya-virus--global-v.1

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A #Market-Based #Sentinel #Surveillance for an Early #Detection of Viral #Outbreaks

 

Abstract

Mexico has experienced recurrent viral epidemics of substantial intensity, including hyperendemic dengue, COVID-19, and recent reports of avian influenza A (H5N1) infections in birds, which pose an ongoing risk of zoonotic transmission. Mexico was also the location for the earliest detection of the pdmH1N1 virus during the 2009 influenza A pandemic. Under a One Health framework, markets represent a unique opportunity for low-cost virus monitoring at the human-animal interface. Under the hypothesis that these represent sentinel sites for an early virus detection, we implemented a pilot surveillance program at the central market of Merida city, Yucatan, Mexico, considered a regional hotspot for multiple and recent viral outbreaks. Longitudinal sampling was carried out over 11 months at 1-to-6-week intervals from April 2022 to February 2023. We used multi-type surveillance in mosquitoes, live poultry, and wastewater. All samples were screened using RT-qPCR. Positive samples for DENV, SARS-CoV-2 and avian influenza A were further sequenced and analysed under a phylogenetic and epidemiological approach. Through our entomological surveillance, we report the earliest detection of DENV-3 III-B3.2 (genotype III American II lineage, considered a major public health concern in Latin America) in Mexico, overlapping with the resurgence of DENV-3 as the predominant serotype driving the 2023 national epidemic, which showed an increased severity. Through wastewater surveillance, we consistently detect SARS-CoV-2 RNA in wastewater samples, coinciding with the two infection waves officially recorded at a city and state level. Finally, cloacal swabs taken from two juvenile birds at the market suggest that avian influenza A viruses circulated in live poultry sold at the market. These findings show that our market-based surveillance framework is effective for an early detection and monitoring of pathogenic viruses in urban settings, and could complement official epidemiological surveillance in low- and middle-income countries to strengthen early-outbreak warning systems.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study was supported by the John Fell OUP Research Grant ATD00390 (M.E.Z and M.U.G.K), the Wellcome Infectious Disease Award ?317324/Z/24/Z (M.G.K, H.P.G and M.E.Z), the Secretaria de Ciencia, Humanidades, Tecnología e Inovación award (SECIHTI, Mexico) through the PRONACES Health grant (PRONAII project number 303002, G.S) and the Ciencia Básica y de Frontera programme (CBF2023-2024-3184, M.G.K), and the UKRI Innovation BSRC/EPSRC/NIHR 971557 grant (A.R.S). M.G.K is funded through a Sanger International Fellowship award. M.E.Z is funded by a UCL Rosetrees Excellence Fellowship UCL2024\2. P.M.D was funded through the doctoral program at ‘Posgrado en Ciencias de la Produccion y de la Salud Animal-UNAM’ through the SECIHTI doctoral scholarship. M.U.G.K. acknowledges funding from The Rockefeller Foundation (PC-2022-POP-005), Health AI Programme from Google.org, the Oxford Martin School Programmes in Pandemic Genomics & Digital Pandemic Preparedness, European Union's Horizon Europe programme projects MOOD (#874850) and E4Warning (#101086640), Wellcome Trust grants 303666/Z/23/Z, 226052/Z/22/Z & 228186/Z/23/Z, the United Kingdom Research and Innovation (#APP8583), the Medical Research Foundation (MRF- RG-ICCH-2022-100069), UK International Development (301542-403), the Bill & Melinda Gates Foundation (INV-063472) and Novo Nordisk Foundation (NNF24OC0094346). B.G is further funded by Wellcome Trust grants 303666/Z/23/Z, 226052/Z/22/Z & 228186/Z/23/Z. The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission or the other funders. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2025.12.22.25342882v1

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Rift Valley #fever [#RVFV] - #Mauritania and #Senegal (#WHO, D.O.N., Nov. 6 '25)

 

Situation at a glance

Between 20 September and 30 October 2025, a total of 404 confirmed human cases of Rift Valley fever (RVF), including 42 deaths, were reported by national health authorities in two West African countries: Mauritania and Senegal. 

RVF is a zoonotic disease, which mainly affects animals, but can also infect humans. 

The majority of human infections result from contact with the blood or organs of infected animals, but human infections have also resulted from the bites of infected mosquitoes. 

To date, no human-to-human transmission of RVF has been documented. 

While RVF often leads to severe illness in animals, its impact in humans varies, ranging from mild flu-like symptoms to severe hemorrhagic fever that can be fatal. 

RVF is endemic in both countries, where recurrent outbreaks have been previously reported in both livestock and humans. 

The risk of further spread remains high, especially with environmental conditions favorable to the proliferation of mosquitoes, periods of heavy rains and increased mosquito activity, as well as movements of livestock within country and towards Mali and Gambia for grazing and trade. 

The response to RVF outbreaks requires a One Health approach, based on enhanced collaboration between the human health, animal health and environmental sectors, in both countries and at the regional level. 

WHO, in collaboration with the World Organization for Animal Health (WOAH), and the Food and Agriculture Organization of the United Nations (FAO), currently assesses the overall risk as high at the national levels, moderate at the regional level and low at the global level.

(...)

Source: World Health Organization, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON584

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Detection of #WNV, #USUV and #Insect-Specific #Bunyaviruses in #Culex spp. Mosquitoes, #Greece, 2024

 

Abstract

Greece is one of the countries in Europe most affected by West Nile virus (WNV), and since 2010, when the virus caused a large outbreak with 197 human neuroinvasive cases, outbreaks occur almost every year. Mosquito surveillance is an indirect sign of virus circulation; therefore, the purpose of the study was the molecular detection of WNV in 45,988 C. pipiens s.l. mosquitoes collected during 2024 in four Regions of Greece and the genetic characterization of the virus strains. WNV was detected in 41 of 1316 (3.12%) Culex spp. mosquito pools. Next-generation sequencing was applied to the WNV-positive samples that had a high viral load. All WNV sequences belong to Cluster B of the sub-lineage Europe WNV-2A presenting a temporal clustering. The WNV infection rates varied highly across the Regions, regional units and months, being higher in Thessaly and Central Macedonia Regions, especially in July and September. All mosquito pools were also tested for Usutu virus (USUV), and one pool was found positive, with sequence clustering into the EU-2 lineage. A subset of mosquitoes (737 pools) was tested for additional viruses, and bunya-like viruses were detected in 6 pools with sequences clustering into four distinct subclades. The prompt detection of pathogenic viruses is helpful for the design of control measures, while the detection of insect-specific viruses provides insights into viral diversity and evolution.

Source: Viruses, https://www.mdpi.com/1999-4915/17/11/1414

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#Italy, Integrated #Surveillance for #WNV & #USUV - Weekly Bulletin No. 10, 18 September '25 (Summary)

 

{Summary}

-- During current epidemiological week (11– 17 September 2025), 65 new confirmed human cases of infection with West Nile Virus have been reported. 

-- The total number of confirmed cases, since the beginning of the epidemic season, has thus risen to 647 (it was 582 last week), of these: 

- 300 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 39 Lombardy, 24 Veneto, 2 Friuli-Venezia Giulia, 1 Liguria, 23 Emilia-Romagna, 5 Tuscany, 83 Latium, 2 Molise, 77 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 19 Sardinia, 

- 54 were asymptomatic cases detected among blood donors, 

- 284 were West Nile Fever cases (one imported from Kenya), 

- 3 asymptomatic cases and 

- 6 unspecified casese. 

-- Among confirmed cases, there were 47 death cases: 7 in Piedmont, 5 Lombardy, 1 Emilia-Romagna, 16 Latium, 15 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases was 15.8% (it was 20% in 2018 and  14% in 2024). 

-- This week nine confirmed cases of Usutu Virus infection have been reported: 2 in Piedmont, 2 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_10.pdf

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The paradoxical #impact of #drought on #WNV #risk: insights from long-term ecological data

 

Abstract

Mosquito-borne diseases are deeply embedded within ecological communities, with environmental changes—particularly climate change—shaping their dynamics. Increasingly intense droughts across the globe have profound implications for the transmission of these diseases, as drought conditions can alter mosquito breeding habitats, host-seeking behaviours and mosquito–host contact rates. To quantify the effect of drought on disease transmission, we use West Nile virus as a model system and leverage a robust mosquito and virus dataset consisting of over 500 000 trap nights collected from 2010 to 2023, spanning a historic drought period followed by atmospheric rivers. We pair this surveillance dataset with a novel modelling approach that incorporates monthly changes in bird host community competence, along with drought conditions, to estimate the effect of drought severity on West Nile virus risk using panel regression models. Our results show that while drought decreases mosquito abundances, it paradoxically increases West Nile virus infection rates. This counterintuitive pattern probably stems from reduced water availability, which concentrates mosquitoes and pathogen-amplifying bird hosts around limited water sources, thereby increasing disease transmission risk. However, the magnitude of the effect depends critically on mosquito species, suggesting species-specific behavioural traits are key to understanding the effect of drought on mosquito-borne disease risk across real landscapes.

Source: Proceedings of the Royal Society B Biological Sciences, https://royalsocietypublishing.org/doi/full/10.1098/rspb.2025.1365?af=R

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#Vectors on the Move: How #Climate Change Fuels the Spread of #Arboviruses in #Europe

 

Abstract

Climate change is increasingly recognized as a major driver of emerging infectious diseases, particularly vector-borne diseases (VBDs), which are expanding in range and intensity worldwide. Europe, traditionally considered low-risk for many arboviral infections, is now experiencing autochthonous transmission of pathogens such as dengue, chikungunya, Zika virus, West Nile virus, malaria, and leishmaniasis. Rising temperatures, altered precipitation patterns, and milder winters have facilitated the establishment and spread of competent vectors, including Aedes, Anopheles, Phlebotomus, and Culex species, in previously non-endemic areas. These climatic shifts not only impact vector survival and distribution but also influence vector competence and pathogen development, ultimately increasing transmission potential. This narrative review explores the complex relationship between climate change and VBDs, with a particular focus on pediatric populations. It highlights how children may experience distinct clinical manifestations and complications, and how current data on pediatric burden remain limited for several emerging infections. Through an analysis of existing literature and reported outbreaks in Europe, this review underscores the urgent need for enhanced surveillance, integrated vector control strategies, and climate-adapted public health policies. Finally, it outlines research priorities to better anticipate and mitigate future disease emergence in the context of global warming. Understanding and addressing this evolving risk is essential to safeguard public health and to protect vulnerable populations, particularly children, in a rapidly changing climate.

Source: Microorganisms, https://www.mdpi.com/2076-2607/13/9/2034

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First Isolation and Characterization of #LiaoNing Virus from #Aedes Vexans #Mosquitoes in #Hokkaido, #Japan, in 2022

Abstract

Background: 

The Liao ning virus (LNV), belonging to the genus Seadornavirus within the family Sedoreoviridae, is a mosquito-borne virus. It was originally isolated from Aedes dorsalis mosquitoes in China. The original LNV strain, LNVS-NE97-31, was reported to infect several mammalian cell lines and cause hemorrhagic symptoms in mice. Subsequently, another LNV strain, LNV NSW B115745, was isolated from Australian mosquitoes; it was reported to exhibit insect-specific infection.

Materials and Methods: 

Virus isolation was performed on mosquitoes collected in northern Hokkaido, Japan, in 2022. The isolated virus was subjected to genomic and growth kinetics analyses.

Results: 

A LNV strain was isolated from Aedes vexans mosquitoes. Genomic sequencing and phylogenetic analysis revealed the new strain as 22WN03, and it formed a robust clade with the original Chinese strain, LNVS-NE97-31. Growth kinetics analysis did not reveal any mammalian or avian cell line susceptible to infection by the strain 22WN03.

Conclusion: 

Overall, the results suggested that the strain 22WN03 has insect-specific infection characteristics, similar to as the Australian strain. Taken together, our findings could expand our knowledge of not only the diversity and geographical distribution of seadornaviruses in Asia but also the ecology of LNV.

Source: Vector-Borne and Zoonotic Diseases, https://www.liebertpub.com/doi/abs/10.1177/15303667251364143

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#Italy, Integrated #WNV & #USUV #Surveillance - Bulletin no. 3, July 31 2025 (IZS Teramo): 57 new human cases reported

{Excerpts}

During the epidemiological week comprised between 24 and 30 July 2025, there were fifty-seven new confirmed cases of human infection with West Nile Virus.

-- Since the start of the epidemic season, eighty-nine cases have been reported (there were thirty-two cases in the last week report), of which:

-- forty were WNND (West Nile Neuroinvasive Disease):

- 2 cases in Piedmont, 1 Lombardy, 3 Veneto, 1 Emilia-Romagna, twenty-three Latium, ten Campania);

-- two cases of asymptomatic infection were detected among blood donors (one in Veneto and one in Campania);

-- forty-six cases of West Nile Fever have been confirmed: 

- one in Lombardy, five in Veneto, thirty-five in Latium, four in Campania, one in Sardinia;

-- one asymptomatic case is from Campania;

-- Among confirmed cases, eight fatalities have been recorded: one in Piedmont, two in Latium and five in Campania. The case-fatality rate among WNND so far is at 20% (during epidemic seasons 2018 it was 20% and in 2024, 14%). 

-- The first case of the 2025 season was reported in Piedmont (a sporadic case in Novara Province). The second case was notified on July 3 in Modena Town. 

-- In the current epidemiological week, no confirmed human cases of infection with Usutu virus have been reported.

(...)

Source: National Veterinary Institute of Teramo, https://westnile.izs.it/j6_wnd/home

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#Italy, West Nile Virus (#WNV) and #Usutu Virus Situation #Report, July 24 '25

{Summary}

-- During the Week 17-23 July 2025, Italy reported twenty-seven new cases of human infection with West Nile Virus.

-- Since the beginning of the epidemic season, thirty-two confirmed human WNV infection cases have been reportede (there were five cases in the last update), of these:

- twenty-three were West Nile Neuroinvasive Disease (WNND): 2 in Piedmont, 2 in Veneto, 1 Emilia-Romagna, 15 Latium, 3 Campania),

- one asymptomatic case was detected in a blood donor (Veneto),

- six cases of West Nile Fever have been reported (2 in Veneto, 4 Latium), and two asymptomatic cases (Latium),

- among the cases, there were two fatalities (1 in Piedmont, 1 in Latium).

-- The first confirmed case of the season was detected in Piedmont Region on March 20 2025 (sporadic case), then in Novara Province (July 3rd).

-- No confirmed cases of Usutu Virus infection have been detected so far.

(...)

Source: Istituto Zooprofilattico Sperimentale di Teramo, https://westnile.izs.it/j6_wnd/home

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Re-Emergence of #Usutu Virus and Spreading of #WestNile Virus #Neuroinvasive Infections During the 2024 Transmission Season in #Croatia

Abstract

Neuroinvasive arboviruses such as tick-borne encephalitis virus (TBEV), West Nile virus (WNV), Usutu virus (USUV), and Toscana virus (TOSV) have (re-)emerged with increasing incidence and geographic range. We analyzed the epidemiology of arboviral infections in Croatia during the 2024 transmission season. A total of 154 patients with neuroinvasive diseases (NID), 1596 horses, 69 dead birds, and 7726 mosquitoes were tested. Viral RNA was detected using RT-qPCR. IgM/IgG-specific antibodies were detected using commercial ELISA or IFA, with confirmation of cross-reactive samples by virus neutralization test. RT-qPCR-positive samples were Sanger sequenced. Arboviral etiology was confirmed in 33/21.42% of patients with NID. WNV was most frequently detected (17/11.03%), followed by TBEV (10/6.49%), USUV (5/3.24%), and TOSV (1/0.64%). WNV infections were reported in regions previously known as endemic, while in one continental county, WNV was recorded for the first time. USUV infections re-emerged after a six-year absence. In addition to human cases, acute WNV infections were recorded in 11/395 (2.78%) of horses and two dead crows. WNV IgG seropositivity was detected in 276/1168 (23.63%) and TBEV IgG seropositivity in 68/428 (15.88%) horses. None of the tested mosquito pools were positive for WNV and USUV RNA. Phylogenetic analysis showed the circulation of WNV lineage 2 and Usutu Europe 2 lineage. Climate conditions in 2024 in Croatia were classified as extremely warm, which could, at least in part, impact the quite intense arboviral season. The spreading of flaviviruses in Croatia highlights the need for continuous surveillance in humans, animals, and vectors (“One Health”).

Source: Viruses, https://www.mdpi.com/1999-4915/17/6/846

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Effectiveness of integrated #vector #management on the incidence of #dengue in urban #Malaysia: a cluster-randomised controlled trial

Summary

Background

Malaysia is one of the southeast Asian countries hardest hit by dengue. We implemented a proactive integrated vector management (IVM) approach in a large non-blinded, cluster-randomised controlled trial to quantify its effectiveness on dengue incidence in urban settings.

Methods

In this cluster-randomised controlled trial we enrolled low-cost and medium-cost residential housing blocks in the Federal Territory of Kuala Lumpur and Putrajaya with recurrent dengue outbreaks. Of the 329 eligible sites, 139 were randomly allocated to receive IVM measures (community engagement, targeted outdoor residual spraying using K-Othrine Polyzone, and deployment of autodissemination devices to target both larval and adult mosquitoes) and 141 received routine vector control activities, stratified by block housing cost. The primary outcome was the comparison of dengue incidence between the two groups using information provided by the national e-Dengue surveillance system. Routine vector control activities continued in both control and intervention sites. The trial was retrospectively registered (ISRCTN81915073).

Findings

Between Feb 10, 2020, and Sept 30, 2022, we carried out our IVM approach in the 139 randomly selected intervention sites. 903 834 individuals (447 149 intervention, 456 685 control) were living in the study areas. Dengue was reported in 1434 individuals in the intervention group (mean incidence per 100 person-years of 0·16 [SD 0·18]) compared with 1663 in the control group (0·18 [0·19; risk ratio 0·86, 95% CI 0·70–1·06; p=0·17). No adverse effects were reported.

Interpretation

Our study did not show an effect on the primary endpoint of the overall dengue incidence. Several factors such as substantial decrease in dengue incidence during the COVID-19 pandemic could have reduced the statistical power to detect significant differences between the two groups. Preventive and long-lasting approaches such as our IVM should be further tested to see if targeted interventions could help limit the number of cases in high-risk transmission areas.

Source: The Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00086-6/abstract?rss=yes

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#Vector competence for #Oropouche virus: A systematic #review of pre-2024 experiments

Abstract {1}

The 2023–24 epidemic of Oropouche fever in the Americas and the associated ongoing outbreak in Cuba suggests a potential state shift in the epidemiology of the disease, raising questions about which vectors are driving transmission. In this study, we conduct a systematic review of vector competence experiments with Oropouche virus (OROV, Orthobunyavirus) that were published prior to the 2023–24 epidemic season. Only seven studies were published by September 2024, highlighting the chronic neglect that Oropouche virus (like many other orthobunyaviruses) has been subjected to since its discovery in 1954. Two species of midge (Culicoides paraensis and C. sonorensis) consistently demonstrate a high competence to transmit OROV (~30%), while mosquitoes (including both Aedes and Culex spp.) exhibited an infection rate consistently below ~20%, and showed limited OROV transmission. Further research is needed to establish which vectors are involved in the ongoing outbreak in Cuba, and whether local vectors and wildlife communities create any risk of establishment in non-endemic regions.

Abstract {2}

Oropouche virus has recently become an urgent threat to public health in Central and South America. OROV is mainly transmitted by biting midges; however, some public health agencies and scientific sources note that some mosquito species transmit the virus. We conducted a systematic review of literature prior to the current epidemic, and identified seven studies that experimentally tested the ability of vectors to become infected with, and transmit OROV (i.e., that assessed their vector competence). These studies have consistently found that biting midges become infected at higher rates than mosquitoes, which rarely transmit the virus. It is unclear which vectors are responsible for transmitting OROV in the current outbreak. Existing published data support the observation that biting midges are likely to be significant vectors compared to mosquitoes, which are comparatively incompetent. However, increased vector surveillance and pathogen testing, and additional vector competence experiments using current OROV strains, are urgently needed.

Source: PLoS Neglected Tropical Diseases, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013014

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Co-Circulation of 2 #Oropouche Virus #Lineages during #Outbreak, #Amazon Region of #Peru, 2023–2024

Abstract

We describe introduction of the 2022–2023 Oropouche virus lineage from Brazil, which has caused large-scale outbreaks throughout Brazil, into the Amazon Region of Peru. This lineage is co-circulating with another lineage that was circulating previously. Our findings highlight the need for continued surveillance to monitor Oropouche virus in Peru.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/4/24-1748_article

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Lack of Competence of #US #Mosquito Species for Circulating #Oropouche Virus

Abstract

Given recent outbreaks of Oropouche virus in Latin America and >100 confirmed travel-associated cases in the United States, we evaluated the competence of US vectors, including Aedes albopictus, Culex quinquefasciatus, Culex pipiens, and Anopheles quadrimaculatus mosquitoes. Results with historic and recent isolates suggest transmission potential for those species is low.

Source: Emerging Infectious Diseases Journal, https://wwwnc.cdc.gov/eid/article/31/3/24-1886_article

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