What we know about Shamonda, the livestock virus linked to a human infection for the first time

French reports said the man in his 60s was severely immunocompromised when he died in early October. World Health Organization said it was an isolated case.

France's report on Thursday of the first known human case of Shamonda, a cattle virus spread by biting midges that reached Europe only this summer, has drawn attention to a pathogen known in livestock since the 1960s but never before found in a person.

The World Health Organization logo at is headquarters in Geneva, Switzerland. (Reuters File Photo)

The patient, a man in his 60s from the Lyon area according to the local newspaper Le Progrès, was severely immunocompromised and was being treated for a serious illness when he died in early October, Reuters reported. French authorities suspect he was infected through a midge bite in eastern France, where the virus circulated among animals in spring and summer. The country's health and agriculture ministries said the neurological complications he developed before his death were "very likely linked" to Shamonda, citing preliminary findings.

The World Health Organization (WHO) described it as an isolated case. The French government said it had identified no health risk to the general population, and the European Centre for Disease Prevention and Control (ECDC) is investigating "the potential public health implications of this first human infection", Bloomberg reported.

The virus

Midges are tiny flies that carry the virus from animal to animal. Cattle are the virus's main hosts, though infections have also been found in sheep, goats, horses and alpacas, according to the World Organisation for Animal Health (WOAH). The midge species behind its spread in Europe is still unknown, Bloomberg reported.

First detected in cattle

Shamonda was first detected in cattle in Nigeria in the mid-1960s. Scientists working in Ibadan described it as a new virus in a 1972 paper on Simbu-group viruses they had isolated there between 1964 and 1969. It has since been reported sporadically in cattle in west, east and southern Africa and in Japan.

In 2015 and 2016, researchers studying cattle in southern Japan found 15 calves born deformed after Shamonda infected them in the womb. The calves had arthrogryposis, a condition in which the joints are locked in bent positions, along with damage to the brain and spinal cord. The researchers concluded that the virus should be treated as teratogenic, or able to cause birth defects, in ruminants such as cattle, sheep and goats.

The virus was confirmed in Europe in late July, after genetic tests on sick cattle in southern Germany, Switzerland and eastern France.

French authorities believe it had been circulating in France since the spring. It has now been detected in 14 countries, among them Austria, Belgium, Ireland, Italy, the Netherlands, Portugal and Spain.

Europe has dealt with a close relative of the virus before. In 2011, farmers and vets in Germany and the Netherlands reported an unidentified disease in cattle, with fever, lower milk yields and diarrhoea. German researchers used metagenomic sequencing, which reads all the genetic material in a sample, to find a new orthobunyavirus in the animals' blood, and first described it as "Shamonda-like" because part of its genome closely resembled Shamonda's.

The virus, named Schmallenberg, spread rapidly across much of central and western Europe in the first known outbreak of a Simbu-group virus on the continent.

The infection

In cattle, Shamonda causes diarrhoea, weakness and loss of appetite and, less often, fever, French animal health authorities said. A study of nine French dairy farms found milk production fell by up to 75%, Reuters reported.

Infection in pregnant cows can cause abortions, stillbirths and brain deformities in calves, according to the Federation of Veterinarians of Europe, Bloomberg reported. Some infected horses have also developed neurological disorders.

WOAH says the long-term impact of the European variants of the virus remains uncertain.

Countries are not obliged to report Shamonda cases to WOAH, because the virus is not on its list of diseases. The European Union's Animal Health Law does not cover it either, so there is no EU surveillance specific to it. The available data therefore may not give a complete picture of its spread, Reuters reported.

The human case

Shamonda had never been detected in a human before the Lyon case, despite circulating in Africa and Asia for decades, the French ministries said. The health ministry called it "an exceptional case involving a severely immunocompromised patient". Clinical, biological and epidemiological investigations are still under way, the ministries said, and doctors have only this one case from which to gauge how the virus affects people.

There is no treatment for the insect-borne orthobunyaviruses that affect livestock, according to a 2022 review of vaccine research published in the journal One Health Outlook. Three vaccines against Schmallenberg have received marketing authorisation for use in livestock, the review added.

A vaccine made for one virus in the group may not protect against another, however. In a 2013 study, researchers vaccinated calves against Akabane and Aino, two relatives of Schmallenberg, and then infected them with Schmallenberg. The vaccine did not prevent infection, and the researchers concluded that vaccines for related viruses could not substitute for ones made specifically for Schmallenberg.

Should people worry?

"Based on current information and knowledge of the transmission of closely related viruses, this is an isolated human case and it is unlikely to lead to wider spread at this time," the WHO said.

In 2012, researchers at the Robert Koch Institute, Germany's national public health agency, surveyed and tested shepherds who had handled sheep infected with Schmallenberg, including birth products carrying high levels of the virus. They found no evidence that the virus had passed to any of them.

But some other viruses in the Simbu group cause human illness. Oropouche, spread mainly by midges, has caused outbreaks in South America and the Caribbean since late 2023, including in places with no previous history of the disease. It has no specific treatment or vaccine, according to the WHO's regional office for the Americas. Shuni, another member of the group, has been found in people with neurological infections in South Africa.

As recently as 2023, researchers who had identified the virus in a goat foetus in South Africa wrote that there was no evidence linking Shamonda to human disease, though they said its characteristics needed study because of the risk that it could pass from animals to people.

Animal diseases and a changing climate

The WHO defines a zoonosis as any disease or infection that passes naturally from vertebrate animals to humans. More than 200 kinds are known, and they account for a large share of new and existing human diseases.

Covid-19 is the most widely studied recent case. In June 2025, the WHO's Scientific Advisory Group for the Origins of Novel Pathogens (SAGO), an independent panel of experts, said available evidence suggested the virus had passed to humans from animals, either directly from bats or through an intermediate host. (There is a longstanding debate on the origins of Sars-CoV-2, the virus that causes Covid-19, with another side supporting a lab-leak theory.)

A 2008 study in Nature of 335 events in which infectious diseases emerged in people between 1940 and 2004 found that 60.3% were zoonoses, most of them originating in wildlife, and that their number had risen over time. Diseases spread by insects and ticks made up 22.8% of the total, and 28.8% in the study's final decade.

Researchers have also linked the risk to how people use land. A 2020 study in Nature found that wild animals known to carry pathogens shared with humans were more common on farmland, in cities and on other heavily used land than in nearby undisturbed habitat, with the effect strongest for rodents, bats and perching birds.

A 2022 study in Nature projected that climate change will bring more wild mammal species into contact with one another, giving viruses new chances to jump between species. By 2070, it found, warming and land-use change will push mammal species into new combinations, including in densely populated parts of Asia and Africa, leading to about 4,000 new transmissions of viruses between species. The authors found that bats would account for most of this sharing, that the shift may already be under way, and that holding warming under 2°C this century would not reduce it.

Since 1998, six strains of bluetongue, a midge-borne livestock disease, have spread across 12 countries and 800km further north in Europe than previously recorded, researchers reported in 2005. They linked the spread to a warmer European climate, which let the virus survive winters better and let its main midge carrier expand northwards, while native European midges began transmitting it too.

These studies aren't specifically about Shamonda. Scientists have not established how the virus reached Europe or which midges are spreading it, and WOAH says its long-term impact remains uncertain.