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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#Oropouche virus #outbreaks in northeast #Brazil between 2024–25 are characterized by sustained #transmission and spread to newly affected areas

 

Abstract

Oropouche virus (OROV) has recently expanded in Brazil, establishing transmission in non-endemic regions. This study aims to integrate epidemiological and molecular data to investigate OROV spread in Northeast (NE) Brazil between 2024 and 2025. OROV cases were analyzed regarding ecological risk factors and geographical clustering. Additionally, we sequenced 65 new OROV genomes from the Northeast states of Pernambuco, Paraíba, and Sergipe to infer the virus’s spatiotemporal dynamics in NE Brazil. A total of 2,806 confirmed cases were reported between March 2024 and April 2025, affecting 170 municipalities across eight out of nine NE states, with highly heterogeneous incidence. An ecological shift was observed, with OROV transmission moving from Atlantic Forest areas in 2024 to humid Caatinga zones in 2025. Phylogenetic reconstruction revealed multiple independent viral introductions in Northeast in 2024, including two in Pernambuco. The first, originating from the central Amazonas, became the main driver of local transmission and subsequently spread to Sergipe and Paraíba, causing outbreaks in 2024 and 2025, respectively. The second introduction remained restricted within Pernambuco. While several Northeast municipalities reported high OROV incidence, Jaqueira (Pernambuco) emerged as a key hub for regional viral spread. OROV showed sustained transmission in the region over a two-year period, characterized by marked spatiotemporal displacement consistent with short-lived, rapidly spreading outbreaks, followed by cryptic transmission and subsequent dissemination to new areas, ultimately driving renewed intense outbreaks.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014171

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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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An ultrapotent #human #antibody neutralizes all maturation states of #Zika virus

 

Significance

Zika virus causes microcephaly in fetuses and no vaccines or therapeutics currently exist against it. Mature and immature flavivirus particles are infectious. Here, we showed the cryoelectron microscopy (cryoEM) structures of an ultrapotent A9E human antibody, complexed with both mature (mZIKV) and immature (immZIKV) Zika virus, and the antibody neutralization mechanism. One important characteristic is that Fab A9E can distort both mZIKV and ImmZIKV particle structures. Additionally, Fab A9E or IgG A9E LALA mutant can abolish or reduce the overall infection to myeloid cells when added to other infection enhancing antibody DV62.5:immZIKV complexes. Thus, antibody A9E represents a promising potential prophylactic and therapeutic candidate, as it is effective against all maturation states of Zika virus.

Abstract

Zika virus (ZIKV), a flavivirus, causes a range of clinical complications including microcephaly in human fetuses. Currently, there is no treatment or vaccine. Different maturation states (mature and immature forms) of flavivirus particles have been observed to be released from infected cells and are infectious. To understand how an ultrapotent human antibody (HMAb) A9E can neutralize these Zika particles, we determined the cryoEM structures of the A9E Fab fragment complexed with mature (mZIKV) and immature (immZIKV) ZIKV to 2.8Å and 7.5Å, respectively. A9E binds to an epitope spanning Domain I (EDI), EDIII, and their linker in an E protein protomer in both immZIKV and mZIKV particles. A9E generally inhibited prior to or during virus attachment to cells, via virus aggregation, distortion of virus particles and inhibition of receptor binding. ImmZIKV is particularly sensitive to structural distortion by Fab A9E. The primary mode of infection used by ImmZIKV is via antibody-dependent enhancement of infection (ADE)—the formation of virus complex with nonneutralizing or subneutralizing concentrations of antibodies, that leads to enhanced infection of Fcγ positive myeloid cells. IgG A9E, by itself displays poor ADE activity. When IgG LALA mutant or Fab A9E is added to other enhancing antibody (DV62.5):virus complexes, they can strongly reduce the overall ADE activity. This is likely due to their ability to distort virus particle structure, suggesting that HMAb A9E could be a potential prophylactic and therapeutic candidate against all maturation states of ZIKV.

Source: 

Link: https://www.pnas.org/doi/abs/10.1073/pnas.2502522122?af=R

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#Kyasanur Forest #disease: an emerging #arboviral #threat

 

Summary

Kyasanur Forest disease is a neglected tick-borne viral haemorrhagic fever endemic to India's Western Ghats, caused by the Kyasanur Forest disease virus, a flavivirus transmitted by Haemaphysalis spinigera ticks. The virus circulates in a sylvatic cycle among monkeys, rodents, shrews, birds, and ixodid ticks, and is transmitted to humans incidentally via tick bites. Since its discovery in 1957 in Karnataka, Kyasanur Forest disease has spread to other Indian states, driven by deforestation, forest fragmentation, and increased human incursion into wildlife habitats. Clinically, the disease manifests in a biphasic pattern, with haemorrhagic and neurotropic presentations. Although a formalin-inactivated vaccine is available, its efficacy is not promising, and no antivirals have been approved to date. Field reports indicate that mortality in monkeys might serve as an early indicator of forthcoming human outbreaks. The transmission dynamics of Kyasanur Forest disease, diagnostic gap, and ecological complexities present substantial public health challenges. In this Review, we provide an update on Kyasanur Forest disease virus, covering its epidemiology, transmission dynamics, molecular virology, virus–host interactions, immunological responses, animal models, and potential antiviral therapies and vaccines.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00589-4/abstract?rss=yes

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#Italy, #WNV & #USUV Integrated #Surveillance - Weekly Bulletin No. 16 - 30 October 2025 (Summary)

 

{Summary}

-- During current epidemiological week (from 23 to 29 Oct. 2025), two new human cases of infection with West Nile Virus have been reported. 

-- The cumulative number of confirmed cases this season so far rose to 773 (they were 771 last week), of these: 

- 367 were West Nile Neuroinvasive Disease (WNND): 17 in Piedmont, 56 Lombardy, 35 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 30 Emilia-Romagna, 11 Tuscany, 1 Marche, 87 Latium, 2 Molise, 83 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 28 Sardinia, 

- 56 were asymptomatic cases detected in blood donors, 

- 339 were West Nile Fever cases (of which: 1 imported from Kenya, 1  from Egypt and 1 from Maldives), 

- 3 asymptomatic cases, 

- 8 unspecified cases. 

-- Among confirmed cases, 72 fatalities have been recorded: 7 in Piedmont, 9 Lombardy, 1 Veneto, 2 Emilia-Romagna, 1 Marche, 19 Latium, 29 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases is 19.6% (it was 20% in 2018, 14% in 2024). 

-- Since the start of the epidemic season, 11 confirmed human cases of Usutu virus infection were reported: 2 in Piedmont, 3 Lombardy, 2 Veneto, 1 Tuscany, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_16.pdf

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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, #WNV & #USUV Integrated #Surveillance - Weekly Bulletin No. 14, 15 Ocotber 2025 (ISS, edited)

 

{Summary}

-- New human cases of West Nile Virus infection continue to be reported albeit with reduced intensity. 

-- During current epidemiological week (from 9 to 15 October 2025) 26 new confirmed cases have been reported. 

-- The total number of cases so far is 767 (they were 740 last week), of these: 

- 366 were West Nile Neuroinvasive Disease (WNND): 17 in Piedmont, 56 Lombardy, 34 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 32 Emilia-Romagna, 10 Tuscany, 1 Marche, 86 Latium, 2 Molise, 83 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 28 Sardinia, 

- 57 were asymptomatic cases among blood donors, 

- 333 were West Nile Fever cases (of which 1 imported from Kenya, 1 from Egypt and 1 from Maldive), 

- 3 asymptomatic cases, 

- eight unspecified cases. 

-- Among confirmed cases, 69 fatalities have been reported: 7 in Piedmont, 9 Lombardy, 2 Emilia-Romagna, 18 Latium, 29 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

-- The case-fatality rate in WNND cases stands at 18.8% (in 2018 it was 20%, in 2024 it was 14%). 

-- So far this season, 10 cases of Usutu virus infection have been recorded: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_14.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 13, 9 October 2025 (Summary): 22 new confirmed cases

{Summary}

-- During current epidemiological week, a rise in the West Nile Virus human cases has been observed although with reduced intensity compared most recent weeks. 

-- Twenty-two new confirmed human cases have been reported during surveillance week from 2 to 8 October 2025. 

-- The cumulative number of cases rose to 740 (they were 718 last week), of these: 

- 354 were West Nile Neuroinvasive Disease (WNND): 16 in Piedmont, 53 Lombardy, 33 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 30 Emilia-Romagna, 11 Tuscany, 1 Marche, 84 Latium, 2 Molise, 81 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 26 Sardinia,

- 57 were asymptomatic cases in blood donors, 

- 318 were West Nile Fever cases, of which 1 imported from Kenya, 1 from Egypt and 1 from Maldives, 

- 4 asymptomatic cases, 

- 7 unspecified cases. 

-- Among confirmed cases there were 68 fatalities: 7 in Piedmont, 9 Lombardy, 2 Emilia-Romagna, 18 Latium, 28 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases is now at 19.2% (it was 20% in 2018 and 14% in 2024). 

-- During current epidemic season, ten Usutu Virus human cases have been confirmed: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_13.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 12, 2 October 2025: 38 new confirmed cases (Summary)

 

{Summary}

-- During current epidemiological week (from 25 September to 1rst October 2025), 38 new confirmed human infection with West Nile Virus have been reported. 

-- Since the beginning of the epidemic season, 718 confirmed cases have been recorded in Italy (they were 680 in the last bulletin), of these: 

- 341 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 51 Lombardy, 30 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 27 Emilia-Romagna, 11 Tuscany, 1 Marche, 84 Latium, 2 Molise, 79 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 2 Sicily, 25 Sardinia, 

- 57 were asymptomatic cases in blood donors, 

- 309 were West Nile Fever cases (1 imported from Kenya, 1 Egypt, and one Maldives), 

- 4 asymptomatic cases, 

- 7 unspecified cases. 

-- Among confirmed cases, there have been 49 fatalities: 7 in Piedmont, 5 Lombardy, 2 Emilia-Romagna, 18 Latium, 14 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases was 14.4% (it was 20% in 2018 and 14% in 2024. 

-- This season 10 confirmed Usutu virus human infections have been recorded: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_12.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 11, September 25 '25 (ISS, Summary)

 

{Summary}

-- During current surveillance week (from 18 to 24 Sept. '25), 33 new confirmed human cases of West Nile Virus have been detected. 

-- Since the beginning of the epidemic season, there have been 680 cases in total, (they were 647 last week); of these: 

- 321 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 44 Lombardy, 27 Veneto, 2 Friuli-Venezia Giulia, 1 Liguria, 25 Emilia-Romagna, 8 Tuscany, 1 Marche, 83 Latium, 2 Molise, 79 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 24 Sardinia), 

- 54 were asymptomatic cases in blood donors, 

- 296 were West Nile Fever cases (1 imported from Kenya, 1 Egypt and 1 Maldives), 

- 3 asymptomatic cases,  

- 6 unspecified cases. 

-- Among confirmed cases, there were 48 deaths: 7 in Piedmont, 5 Lombardy, 2 Emilia-Romagna, 17 Latium, 14 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate among WNND cases was 14.9% (it was 20% in 2018 and 14% in 2024). 

-- During current surveillance week, nine new confirmed human cases of Usutu virus have been confirmed: 2 in Piedmont, 2 Lombardy, 2 Veneto, 3 Latium).

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_11.pdf

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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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#Italy, Integrated #Surveillance for #WNV & #USUV - Weekly Bulletin No. 9, 11 September '25 (summary): 80 new cases

{Summary}

-- During current epidemiological week (4 to 10 September), eighty new confirmed human cases of West Nile Virus infection have been reported in Italy.

-- Since the beginning of the epidemic season, there have been a total of 582 confirmed cases (they were 502 last week), of these: 

- 260 were West Nile Neuroinvasive Disease (WNND): 14 in Piedmont, 24 Lombardy, 22 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 20 Emilia-Romagna, 3 Tuscany, 77 Latium, 2 Molise, 74 Campania, 1 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 13 Sardinia, 

- 48 asymptomatic cases among blood donors, 

- 262 cases of West Nile Fever (1 imported from Kenya), 

- 4 asymptomatic cases, 

- 8 unspecified cases. 

-- A total of 39 fatal cases have been reported so far this season: 5 in Piedmont, 2 Lombardy, 1 Emilia-Romagna, 15 Latium, 14 Campania, 2 Calabria. 

- The Case-Fatality Rate among WNND cases is thus far at 15% (during 2018 season it was 20%, in 2024 14%). 

-- During current surveillance week there were 7 new confirmed Usutu Virus infection cases: 2 in Piedmont, 2 Lombardy, 1 Veneto, 2 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_09.pdf

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Shared viral burdens: Evidence of active #Usutu virus circulation and multi- #arbovirus exposure in migrant and resident #birds at wintering locations in #Nigeria

 

Abstract

Background: 

West Nile (WNV), Usutu (USUV), and Sindbis (SINV) virus were initially detected in the African region, and subsequently across temperate regions where they were absent. Wild birds are primary reservoirs for these arboviruses and are considered major contributors to their global spread through seasonal migration. To understand the transmission dynamics of arboviruses in wild birds and the potential of migratory birds to spread the viruses at an intercontinental scale, we investigated arboviral infections and exposures in African resident and Palearctic migratory birds at wintering locations in Nigeria. 

Methodology/Principal Findings: 

Oropharyngeal- and cloacal swabs, feathers and blood were collected from resident and migratory birds at two wintering locations (Amurum and Ngel-Nyaki Forest Reserves). Swabs and feathers were tested using RT-PCR for WNV, USUV and SINV, and blood with ELISA and FRNT90 or PRNT80 for antibodies. 573 birds were sampled between 2021 to 2024 across months coinciding with arrival and departure of migratory birds. USUV RNA was detected in 2.6% of feathers including a positive Icterine warbler and a garden warbler sampled prior to spring migration. None of the swabs was positive for viral RNA but neutralizing antibodies to WNV and USUV were detected in 4.5% of birds. SINV antibodies were also found in 34.1% of birds sampled across the wintering locations. 

Conclusions/Significance: 

Our findings showed that migratory birds can become infected with USUV, and potentially with WNV and SINV during their overwintering periods in Africa and highlighted a wider arbovirus risk in Nigeria. In addition, detections of viral RNA in feathers, but not swabs, suggest feathers may be a suitable matrix for surveillance in the absence of a reliable cold chain. The overall detections in wild birds at these locations highlight the need for further surveillance to define the epidemiology and public health risks of these arboviruses in the region.

Competing Interest Statement

The authors have declared no competing interest.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.09.08.674803v1

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#Italy, Integrated #WNV & #USUV Viruses #Surveillance - Weekly #Bulletin No. 8, September 4 2025 (summary)

{Summary}

-- During current surveillance week (28 August - 3 September 2025): 

- 72 new confirmed human cases of West Nile Virus infection have been confirmed; 

-- The total number of cases since the beginning of epidemic season has risen to 502 (they were 430 in the last bulletin); of these: 

- 226 were West Nile Neuroinvasive Disease (WNND): 11 in Piedmont, 16 in Lombardy, 17 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 15 Emilia-Romagna, 3 Tuscany, 71 Latium, 2 Molise, 72 Campania, 1 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 8 Sardinia, 

- 40 were asymptomatic cases detected in blood donors, 

- 226 were West Nile Fever cases (one of them imported from Kenya),

- 5 asymptomatic cases, 

- 5 unspecified. 

-- So far there have been 33 fatal cases: 3 in Piedmont, 1 Lombardy, 1 Emilia-Romagna, 14 Latium, 12 Campania, 2 Calabria. 

- The Case-Fatality rate among WNND cases is thus far at 14.6% (in 2018 it was 20%, in 2024 14%). 

-- During current surveillance week, there have been 4 confirmed Usutu virus human infections: 2 in Piedmont, 1 Veneto, 1 Latium).

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_08.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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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly #Bulletin No. 7 - 28 August 2025 (summary)

 

{Summary}

-- During surveillance week from 21 to 27 August, 79 new confirmed human cases of West Nile Virus infection have been reported. 

-- Since the beginning of the epidemic season, the total number of confirmed cases have risen to 430 (they were 351 in the last bulletin); of these:

- 193 were West Nile Neuroinvasive Disease cases: 8 in Piedmont, 12 Lombardy, 14 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 13 Emilia-Romagna, 62 Latium, 2 Molise, 64 Campania, 2 Basilicata, 5 Calabria, 1 Sicily, 8 Sardinia), 

- 38 were asymptomatic cases among blood donors, 

- 193 were West Nile Fever cases, 

- 3 asymptomatic and 

- 3 unspecified cases. 

-- Among the confirmed cases, there were 27 fatalities: 1 Piedmont, 1 Lombardy, 1 Emilia-Romagna, 11 Latium, 11 Campania, 2 Calabria). 

- The Case-Fatality Rate in WNND cases is so far at 13.9% (during 2018 it was 20%, in 2024 14%). 

-- One confirmed human case of Usutu virus infection has been confirmed in Latium's province of Latina. 

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_07.pdf

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Serological #Evidence of #Flavivirus #Infection Among #Mothers of #Newborns in El Paso, #Texas

 

Abstract

Background: 

Flaviviruses represent a significant worldwide threat to human health and have the potential to emerge and cause outbreaks in non-endemic geographical regions. Ongoing surveillance for these viruses in the United States–Mexican border communities such as El Paso, Texas, is lacking. As a continuing effort to better understand the prevalence and to determine which arboviruses are endemic, the aim of this study was to determine the prevalence rate of specific flavivirus antibody among 910 human umbilical cord blood samples obtained from mothers who delivered newborns in El Paso, Texas.

Materials and Methods: 

The samples were screened for West Nile virus (WNV) and dengue virus (DENV) IgG antibodies with an enzyme-linked immunosorbent assay and confirmed by a plaque reduction neutralization test for DENV, WNV, Zika virus (ZIKV) and Saint Louis encephalitis virus (SLEV).

Results: 

Among the 910 samples, 2% were positive for specific IgG antibody to DENV, 4.4% to WNV, 0.1% to SLEV, and 0.0% for ZIKV antibody. The results confirmed the local transmission of WNV and supported a low prevalence rate for DENV, and this was the first reported serological evidence of SLEV infection in the El Paso community.

Conclusion: 

The interpretation of the public health significance of these observations supported previous findings of ongoing transmission of WNV and suggested the possibility of DENV transmission and re-emergence of SLEV in the community. Therefore, prospective studies are needed to obtain a more conclusive understanding of the prevalence of flaviviruses in the El Paso community.

Source: Vector-Borne and Zoonotic Diseases, https://www.liebertpub.com/doi/abs/10.1177/15303667251367518

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#Italy, Integrated #Surveillance for #WNV and #USUV - Weekly #Bulletin no. 6 - August 21 2025 (summary): 76 new cases, total so far 351

{Summary}

-- During current surveillance week (14 to 20 August), seventy-six new human confirmed cases of West Nile Virus infection have been reported;

-- So far this year, 351 human cases of WNV infection were confirmed (they were 275 last week); of these:

- 158 were WNND (West Nile Neuroinvasive Disease): 6 in Piedmont, 8 Lombardy, 10 Veneto, 1 Friuli-Venezia Giulia, 8 Emilia-Romagna, 59 Latium, 54 Campania, 2 Basilicata, 5 Calabria, 5 Sardinia;

- 27 were asymptomatic cases in blood donors, 

- 162 were West Nile Fever cases, 

- 2 asymptomatic and 

- 2 symptomatic (unspecified). 

-- Among confirmed cases, there were 22 fatalities: 1 in Piedmont, 1 Lombardy, 10 Latium, 9 Campania, 1 Calabria). 

- The Case-Fatality Rate in WNND cases is thus far at 13.9% (in 2018 it was 20%, and in 2024, 14%). 

-- No confirmed cases of Usutu Virus infection have been confirmed this week.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_06.pdf

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#Italy, #WNV and #Usutu Virus Weekly #Surveillance #Bulletin No. 4, July 7 '25: 84 new confirmed cases (ISS)

{Summary}

-- Since the last update (July 31), eighty-four new confirmed cases of human infection with West Nile Virus have been reported. 

-- Since the start of epidemic season, there were 173 confirmed WNV cases, of which: 

- 72 were West Nile Neuroinvasive Disease (WNND): (2 in Piedmont, 2 Lombardy, 4 Veneto, 1 Friuli-Venezia Giulia, 2 Emilia-Romagna, 37 Latium, 21 Campania, 1 Basilicata, 1 Sardegna), 

- 14 were asymptomatic cases in blood donors, 

- 85 were West Nile Fever cases, 

- 1 was an asymptomatic case 

-- Among the confirmed cases, there were eleven fatalities: 1 in Piedmont, 4 Latium, 6 . 

- The case-fatality rate among WNND cases is at 15% (during 2018 season it was 20%, whereas in 2024 it was 14%). 

-- No new confirmed cases of Usutu Virus human infection have been reported during current surveillance week.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_04.pdf

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