First Human Shamonda Virus Death Confirmed in France

France reported the world's first laboratory-confirmed human infection with Shamonda virus (SHAV) on 20 October 2026, and the patient — an immunocompromised older adult male — died on 8 October after developing severe encephalitis.

The man was hospitalized in rural eastern France on 18 August 2026 for an underlying illness. Neurological signs began on 23 September: visual disturbances, confusion, loss of consciousness and seizures. Clinicians diagnosed severe encephalitis on 25 September and collected cerebrospinal fluid (CSF) samples.

Metagenomic sequencing of those CSF samples identified SHAV, and French health authorities were notified on 7 October. The sequence belonged to the SHAV-EU1 genotype and was 99% genomically identical to a virus circulating in Switzerland; the retrieved sequence covered roughly 90% of the genome. A broad panel of tests for other encephalitis pathogens returned negative results.

How investigators ruled out other routes

Retrospective RT-PCR testing confirmed SHAV RNA in serum samples collected from early July through October, and in faecal, urine, saliva and respiratory samples. Post-mortem biopsies of the brain, liver and spleen showed very high viral genomic loads.

The patient had not travelled in the preceding year and lived where animal SHAV transmission had been documented since July 2026. He had received multiple blood transfusions between February and October 2026. Testing by the French Blood Establishment (EFS) and the National Reference Center for Arboviruses (CNR) on donors linked to transfused red cell units was negative, making transfusion-associated transmission unlikely but not completely excluded. Epidemiological investigations found no specific source of exposure, although mosquito exposure was reported. Serological testing of close contacts is under way.

The takeaway: transmission route remains unknown, and vector-borne acquisition remains a plausible but unproven hypothesis.

What is happening in European livestock?

SHAV belongs to the family Peribunyaviridae, genus Orthobunyavirus, within the Simbu serogroup — the same species as Schmallenberg virus (Orthobunyavirus schmallenbergense). It was first isolated from cattle in Nigeria in the 1960s and later found in animals in parts of Africa, Japan and Europe.

The virus surfaced in Europe in summer 2026, with confirmed or suspected infections in cattle, horses and alpacas in Belgium, France, Germany, the Netherlands and Switzerland. By 21 October 2026, Austria, Ireland, Jersey, Liechtenstein, Portugal, Slovenia and Spain had also reported animal detections. In metropolitan France alone, animal detections spanned 54 departments as of 20 October, predominantly in cattle.

Two variants circulate in animals: SHAV-EU1 in Germany, Austria, France and Switzerland, and SHAV-EU2 in Belgium, the Netherlands, northern Germany and northwestern France.

What changes at the exam table and in the barn

SHAV is considered vector-borne, not spread directly between animals. The presumed primary vectors are biting midges of the genus Culicoides, though the main vector species remain unknown. Wind-assisted dispersal of infected midges may introduce the virus into new areas, and vertical transmission from dam to fetus during gestation can occur.

In cattle, reported signs include fever, diarrhoea, reduced activity and appetite, and reduced milk production. Horses have shown neurological disease with SHAV-positive brain tissue. Congenital malformations are documented for related Simbu serogroup orthobunyaviruses; the effects of the European SHAV strains on pregnancy and fetal development require further study.

No specific antiviral treatment or vaccine exists for SHAV. Prevention in animals rests on reducing midge exposure, livestock management and routine farm biosecurity. Laboratory confirmation relies on RT-PCR, with sequencing where indicated.

The practical point: with bluetongue virus circulating concurrently in Europe and clinical signs overlapping, differential diagnosis is essential.

WHO also flags an equine surveillance opportunity: retrospective investigation of horses with SHAV-compatible signs that tested negative for West Nile virus (WNV), plus testing of WNV-positive horses for possible co-infection, would clarify SHAV's role in European equine disease.

What is the regulatory and public-health position?

As of October 2026, SHAV is not on the World Organisation for Animal Health (WOAH) list of reportable diseases. However, where SHAV meets the definition of an emerging disease, veterinary authorities must notify WOAH under Article 1.1.5 of the Terrestrial Health Code.

Foodborne transmission is currently considered unlikely. Even so, investigations are assessing potential SHAV excretion in the milk of infected cattle and any implications for food safety — a question of direct relevance to dairy operations in affected regions.

On the human side, WHO states that a single case cannot establish the risk to the general population, the frequency of infection, or its clinical spectrum. Human transmission by Culicoides is documented for Oropouche virus, another orthobunyavirus, but no evidence currently supports that route for SHAV. Seasonal declines in midge activity may reduce transmission short-term in northern climates without excluding other routes.

WHO recommends:

• Continued animal surveillance and consideration of human serosurveys, with timely information sharing between veterinary and public health authorities.
• Investigation of the source of the French case, including vector exposure.
• Further viral genotype and phenotype analysis to assess human transmission potential.
• Testing for SHAV in people with compatible symptoms and relevant occupational or environmental exposure.
• Strengthened entomological studies to identify vector species, seasonal dynamics and vector competence.
• One Health investigations in animal populations, including sentinel species.
• Risk communication that clearly separates established animal circulation from still-limited evidence of human infection.

WHO will update its risk assessment if additional human infections appear, the transmission route is clarified, or new evidence emerges on outcomes in immunocompromised and immunocompetent individuals. For veterinary practices across Europe, the immediate task is surveillance, differential diagnosis of neurological and systemic cases, and coordination with public health authorities as the evidence base develops.