France has reported the first documented human infection with Shamonda virus, a pathogen previously detected only in animals, raising questions about its potential risks to public health.
The World Health Organisation (WHO) confirmed the case on Thursday, October 22, saying the patient had a weakened immune system and died after contracting the virus.
The case is drawing attention to Shamonda virus because it had not previously been recognised as a cause of human disease, despite circulating among animals for decades.
The WHO said there was no identified public health risk to the general population based on current knowledge, while investigations continue to establish how the patient became infected.
Here is what to know about the virus, how it spreads and the risks it poses to humans and animals.
What is Shamonda virus?
Shamonda virus is a virus that belongs to a group known as Orthobunyavirus. It is primarily associated with livestock, particularly cattle, although infections have also been reported in sheep, goats and horses.
The virus was first isolated from cattle in Nigeria in 1965 and has since been detected sporadically in parts of Africa and Asia, including Japan.
It was detected in European livestock for the first time in 2026, before French authorities reported the first documented human infection. The virus belongs to the same broader group as Schmallenberg virus, which is known to cause reproductive problems and birth defects in livestock.
According to the World Organisation for Animal Health (WOAH), the full effects of the variants detected in Europe remain uncertain.
How does Shamonda virus spread?
Shamonda virus is believed to spread mainly through the bites of infected Culicoides midges, tiny biting insects that resemble flies.
These insects transmit the virus between susceptible animals. The exact route through which the French patient became infected is still being investigated, although authorities suspect transmission through a midge bite.
The patient had been in an area of eastern France where the virus was circulating among animals and where the biting midges were present.
Scientists are investigating the circumstances of the infection to establish whether the virus can be transmitted to humans through other routes.
There is currently no evidence that Shamonda virus spreads directly from one person to another. However, the available evidence on human infection remains limited because this is the first documented case.
What happened in the first human case?
The first documented human infection was identified in France in a patient who was receiving treatment for a serious illness at a hospital in Lyon.
The patient had a severely weakened immune system, a condition that made them more vulnerable to infections and potentially severe complications.
French authorities reported that the patient died in early October. Investigations indicated that complications affecting the brain were likely linked to the infection, although assessments of the case and the circumstances surrounding the death are continuing.
Tedros Ghebreyesus, WHO Director-General said the organisation was working with French authorities to establish the source of the infection, possible routes of transmission and any implications for public health.
The case is significant because Shamonda virus had previously been considered incapable of causing human infection.
What are the symptoms of Shamonda virus?
The symptoms of Shamonda virus infection in humans are not yet well established because no human cases had previously been documented.
In animals, reported signs include fever, diarrhoea and reduced milk production in cattle. Infection has also been associated with reproductive problems, including abortions and abnormalities in developing foetuses.
Neurological disorders have been reported less commonly in some animals, including horses.
The French patient experienced serious complications, including problems affecting the brain. However, the case involved a person with a severely weakened immune system, and scientists are still investigating the relationship between the infection and the complications.
According to experts, it would therefore be premature to use the symptoms observed in this single case to define how the virus might affect other people.
How dangerous is Shamonda virus to humans?
The risk to humans remains uncertain because the available evidence is limited. The death of the French patient has raised concerns, but health authorities have emphasised that the case was exceptional and involved a person whose immune system was severely weakened.
WHO is investigating the case to determine how the patient was infected and whether there are any wider implications for public health.
The available evidence does not establish that Shamonda virus spreads readily among humans or that it poses a threat comparable to viruses known to cause sustained human-to-human transmission.
Can Shamonda virus be prevented or treated?
There is currently no commercially available vaccine specifically for Shamonda virus, according to WOAH.
Because the virus is primarily associated with animals and biting midges, control measures focus on monitoring livestock and reducing exposure to the insects that transmit it.
Veterinary authorities can strengthen surveillance, investigate suspected infections and reproductive problems in livestock, and take measures to reduce midge exposure where necessary.
For humans, there is not yet enough evidence to recommend a specific prevention programme against Shamonda virus. The most important immediate step is continued investigation by health and veterinary authorities to understand how the first infection occurred.
Should Nigerians be worried?
Shamonda virus was first isolated in cattle in Nigeria in 1965, but this historical discovery does not mean that the country is currently experiencing an outbreak of the virus in humans.
The French case is the first documented human infection, and health authorities have not identified a public health risk to the general population at this stage.
According to experts, the development highlights the importance of monitoring animal diseases, investigating unusual infections and strengthening cooperation between human and animal health authorities.
The current priority is to establish how the French patient became infected and improve scientific understanding of Shamonda virus.
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