Shamonda virus in human - France

On 20 October 2026, the National IHR Focal Point (NFP) of France notified WHO regarding the first documented human infection with Shamonda virus (SHAV). The case was an immunocompromised older man from eastern France with no travel history during the preceding year. He developed severe neurological illness on 23 September 2026 and was diagnosed with severe encephalitis (brain inflammation). The patient died on 8 October 2026. SHAV is recognized primarily as an animal-associated virus, like the closely related Schmallenberg virus circulating in Europe, with no previously documented human infections. SHAV was confirmed by metagenomic sequencing and reverse transcription polymerase chain reaction (RT-PCR), with high viral loads detected in tissue samples collected after death and other causes of encephalitis excluded. There is currently widespread SHAV circulation in animals in Europe, including outbreaks across much of France. The source and route of human infection remain unknown. While vector-borne transmission is most likely, food-borne transmission is under investigation. As this is the first documented laboratory confirmed human infection, WHO considers that the public health risk cannot yet be reliably assessed and recommends continued One Health surveillance and investigation.

On 20 October 2026, the National IHR Focal Point of France notified WHO of a laboratory-confirmed human infection with Shamonda virus. The case was an immunocompromised older adult male who was hospitalized on 18 August 2026 for his underlying illness. He developed neurological signs on 23 September, including visual disturbances, confusion, loss of consciousness and seizures. A diagnosis of severe encephalitis was made on 25 September, and cerebrospinal fluid (CSF) samples were collected. He died on 8 October.

Virological findings of SHAV were identified by metagenomics on the CSF samples from 25 September, and the French health authorities were notified on 7 October. The sequence belonged to the SHAV-EU1 genotype and is 99% genomically identical to a virus circulating in neighbouring Switzerland, and the sequence retrieved covered approximately 90% of the genome. Retrospective testing of serum samples collected in early July through October, as well as faecal, urine, saliva and respiratory samples, confirmed the presence of SHAV RNA by RT-PCR. Post-mortem biopsies of the brain, liver and spleen showed very high viral genomic loads. A wide panel of tests for other encephalitis pathogens returned negative results. The patient lived in rural eastern France, where animal SHAV transmission has been documented since July 2026, and had not travelled in the preceding year. The patient received multiple blood transfusions between February and October 2026 for his underlying illness.

Testing performed by the French Blood Establishment (EFS) and the National Reference Center for Arboviruses (CNR) on blood donors linked to transfused red blood cell units was negative for Shamonda virus, making transfusion-associated transmission unlikely, although it cannot be completely excluded at this stage. Epidemiological investigations around the case have not identified a specific source of exposure, although mosquito exposure was reported. Serological investigations are also being conducted among close contacts of the patient.

Although foodborne transmission is currently considered unlikely, investigations are ongoing to assess the potential excretion of Shamonda virus in the milk of infected cattle and to better characterize any potential implications for food safety. In parallel, veterinary and entomological investigations are continuing to further clarify the vector(s), the ecology, transmission pathways, and public health significance of the virus.

This is the first laboratory confirmed human case of Shamonda virus disease reported globally. No additional human cases have been detected to date.

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

Until the recently reported human case, SHAV was recognized primarily as an animal-associated virus, like the closely related Schmallenberg virus circulating in Europe, with no documented human infections. As this is the first confirmed human infection reported globally, there is currently insufficient evidence to assess the extent to which SHAV infects humans or causes disease.

SHAV was detected for the first time in Europe during the summer of 2026 with confirmed or suspected infections reported in cattle, horses and alpacas in Belgium, France, Germany, the Netherlands and Switzerland. As of 21 October 2026, additional European countries and territories have reported SHAV detections in animals: Austria, Ireland, Jersey, Liechtenstein, Portugal, Slovenia and Spain. In metropolitan France, as of 20 October, the available reports indicate animal detections in 54 departments, predominantly in cattle.

Two distinct variants of SHAV have been identified in animals in Europe: SHAV-EU1, reported in Germany, Austria, France and Switzerland, and SHAV-EU2, identified in Belgium, the Netherlands, northern Germany and northwestern France. 

Based on current knowledge, SHAV is a vector-borne disease and it is not considered to spread directly between animals. It appears to be transmitted primarily by biting midges of the genus Culicoides, although the main vector species remain unknown. Culicoides (midges) are widespread, and climate change may alter their geographical distribution and abundance, potentially affecting the transmission of vector-borne pathogens in Europe, including Simbu serogroup orthobunyaviruses such as Schmallenberg virus, as well as orbiviruses like bluetongue and African horse sickness viruses. Furthermore, wind-assisted dispersal of infected Culicoides over long distances may also contribute to the introduction and spread of midge-borne viruses into previously unaffected areas, although its role in SHAV transmission requires further investigation. Vertical transmission from mother to fetus during gestation in animals can also occur.  

In cattle, reported signs include acute systemic illness, such as fever, diarrhoea, reduced activity or appetite, and reduced milk production. Neurological disease has been observed in horses with SHAV-positive brain tissue. Congenital malformations have occurred during gestational infection with related Simbu serogroup orthobunyaviruses in animals. However, the full effects of SHAV, including recently detected European strains, on pregnancy, reproduction and fetal development in animals require further investigation. 

Given the concurrent circulation of bluetongue virus in Europe and the overlap in clinical signs, veterinary surveillance and laboratory-based differential diagnosis are important. Laboratory confirmation relies on molecular methods, such as RT-PCR, with sequencing or further testing where indicated. No specific antiviral treatment or vaccine is currently available for SHAV; animal-health prevention measures focus on reducing exposure to biting midges, livestock management practices and routine farm biosecurity. 

Given the potential for overlapping neurological or systemic clinical presentations in animals with other viral infections, such as West Nile virus (WNV), retrospective investigations may be warranted among equine cases presenting with clinical signs compatible with SHAV infection that tested negative for WNV. In addition, testing of samples from WNV-positive horses could help assess the occurrence of possible co-infections and better characterize the contribution of SHAV to equine disease. Such investigations would support a more accurate assessment of the epidemiology, clinical impact and geographical distribution of SHAV in the European equine population.

The emergence of SHAV in Europe warrants continued epidemiological surveillance and assessment by national veterinary authorities and the public health authorities in Europe using a coordinated One Health approach.  As of October 2026, SHAV was not included in the World Organisation for Animal Health (WOAH) list of reportable diseases; however, where SHAV meets the definition of an emerging disease, veterinary authorities are required to notify WOAH in accordance with Article 1.1.5 of the Terrestrial Health Code. 

• Notification by authorities to WHO and regional bodies. 
• Clinical, biological and epidemiological investigations are continuing in conjunction with experts in human, animal and environmental health.

This first documented human infection with SHAV in 2026 demonstrates that human infection is possible. However, a single case is insufficient to assess the risk to the general population, including immunocompetent individuals, or to determine the frequency, clinical spectrum or severity of human infection. The route of infection and possible sources of exposure are unknown, though vector-borne transmission is a plausible hypothesis.

Although transmission to humans by Culicoides has been documented for Oropouche virus, another orthobunyavirus, currently, there is no evidence that SHAV is transmitted to humans by this route. Although widespread animal infections in Europe justify further investigation of potential human exposure, they do not establish the likelihood of human infection or sustained transmission. Seasonal declines in Culicoides activity may reduce vector-borne transmission in the short term in northern climates, but do not exclude other routes or future exposure. 

Given the very limited data regarding the zoonotic potential of SHAV, the public health risk remains uncertain and cannot yet be reliably assessed or quantified. Continued surveillance, investigation of potential transmission routes and potential new human cases, assessment of clinical outcomes across different population groups and retrospective studies in animal populations are warranted. The risk assessment should be updated as further evidence becomes available. 

In view of the limited evidence on the zoonotic potential of SHAV, the following actions are recommended:

• Strengthened surveillance and information sharing. Continue animal surveillance for SHAV and other orthobunyavirus and consider appropriate human surveillance such as serosurveys, with timely information sharing between veterinary and public health authorities. Suspected human infections should be investigated in accordance with national procedures and available diagnostic capacity.
• Further investigation of the circumstances surrounding the reported case should seek to clarify the source of infection, including the potential contribution of vector exposure.
• Assessment of the potential for infection across different population groups. Further analysis of viral genotype and phenotype is required to better understand its potential for transmission to humans.
• Should additional human cases be identified, investigations should aim to characterize clinical presentation and outcomes, taking account of immune status and relevant underlying conditions or treatments.
• Improved diagnostic and epidemiological understanding, including laboratory investigation and characterization of any suspected cases.  SHAV should be considered and tested for in people with relevant symptoms when occupational and/or environmental exposure may be compatible, until the risk to humans is better understood. Collaboration between human and animal health services can help identify possible epidemiological links and improve understanding of the virus's transmission pathways.
• Strengthened entomological investigations. Entomological studies should be enhanced to identify the Culicoides species and potentially other vectors involved in SHAV transmission and assess their geographical distribution, seasonal dynamics and vector competence. Improved understanding of the vectors involved would support both animal and public health risk assessments and help inform surveillance prevention and control strategies.
• Promoting One Health investigations to better characterize SHAV circulation. Investigations in animal populations, including species that may serve as sentinels of viral circulation, can provide valuable information on the geographical spread, transmission dynamics and clinical impact of SHAV. Improved understanding of animal infections may help identify areas of possible human exposure and support public health risk assessment.
• Maintaining proportionate risk communication. Communication should clearly distinguish the established circulation of SHAV in animals from the still-limited evidence of human infection.
• Review the risk assessment as evidence evolves. The assessment should be updated if additional human infections are identified, the route of transmission is clarified, or new evidence emerges regarding the clinical consequences of infection in immunocompromised or immunocompetent individuals. 

Continued surveillance, targeted investigation and coordination between human and animal health authorities are warranted to address uncertainties and inform any subsequent adjustment of public health risk assessment and guidance.