France reports first documented human infection with Shamonda virus; patient dies

French authorities have reported the first documented human infection with Shamonda virus in a severely immunocompromised patient who died in early October, prompting investigations by French health officials, the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC).

The patient had been receiving treatment for a serious illness at Hospices Civils de Lyon, a public hospital group in Lyon. French authorities said the infection was an exceptional case and that, based on current knowledge, no health risk to the general population had been identified.

The French Agriculture Ministry said clinical, laboratory and epidemiological investigations were continuing to establish how the patient acquired the infection and whether the virus caused or contributed to the death.

“According to investigations carried out so far, the brain complications observed in the immunocompromised patient before their death were very likely linked to the Shamonda virus infection,” the ministry said.

WHO and European health agency investigate transmission

WHO Director-General Tedros Adhanom Ghebreyesus said on Thursday that the organisation was working with French authorities to determine how the infection occurred and assess potential public health risks.

In a post on X, Tedros said French officials were gathering information about the source of the infection and possible ways the virus could spread. He noted that the patient had a weakened immune system that increased their vulnerability to severe illness.

“The French patient was in an area where the Shamonda virus was circulating in animals and where Culicoides midges were also present,” Tedros said.

French authorities suspect the patient was infected through the bite of a Culicoides biting midge in eastern France, where the virus had been detected in animals during spring and summer 2026.

However, the specific midge species involved in the suspected transmission has not been identified, according to the ECDC.

The ECDC said it was in contact with French authorities and European partners to investigate the potential public health implications. It is also working with the relevant European Union reference laboratory to strengthen testing capacity and support member states in identifying any additional potential cases.

The investigations are being conducted under a One Health approach, which considers human, animal and environmental health together. French authorities have notified the WHO and ECDC of the case.

Virus previously detected in animals, including cattle

Shamonda virus, also known as SHAV, is an Orthobunyavirus transmitted to animals by biting midges of the genus Culicoides. Until this case, it had been considered non-transmissible to humans, and no human infection had been documented despite decades of circulation in Africa and Asia.

The virus was first detected in Nigeria in the mid-1960s and has since been reported sporadically in cattle in West, East and southern Africa, as well as in Japan.

Cattle are considered the main animal hosts, although sporadic infections in small ruminants and horses were also reported in France during summer 2026.

In infected adult cattle, symptoms can include fever, lethargy and diarrhoea. Dairy cows may also experience a significant decline in milk production, according to Sciensano, Belgium's national public health institute.

The virus was detected in European farm animals for the first time in summer 2026. Clinical signs in animals were reported from June, and the virus was identified in late July.

Since then, infections have been detected in farm animals in Austria, Belgium, France, Germany, Ireland, Italy, Liechtenstein, Luxembourg, the Netherlands, Portugal, Spain and Switzerland, as well as on the Channel Island of Jersey.

Biting midge activity declines as temperatures cool

Shamonda virus typically spreads between animals through the bites of infected Culicoides midges. These small flying insects are generally most active in Europe from spring to autumn, although activity varies by species, location and weather conditions.

The ECDC said activity among most biting midge species was declining as temperatures cooled across Europe.

The agency is monitoring developments in coordination with the European Commission and the European Food Safety Authority, which covers animal health and food safety across the European Union.

Although the virus has now been documented in a human for the first time, French authorities said the case involved a patient with severe immunosuppression and that no risk to the general population had been identified based on current knowledge.

Investigations remain under way to clarify the route of infection and determine the virus's role in the patient's death.