France has reported the first documented human case of the Shamonda virus, which was previously detected only in animals.
The patient was immunocompromised and died, health officials said.
The Shamonda virus is spread by tiny biting flies, which are known as midges.
In animals, the virus has been shown to cause fever, diarrhea, reduced milk production, and reproductive disorders, including abortions and fetal malformations, according to the World Organization for Animal Health.
Because the Shamonda virus has never been detected in humans before, its potential symptoms and effects on human health remain unknown.
This summer, farmers in parts of Europe reported their livestock being infected, including cattle. Other animals like horses, alpacas, sheep, and goats can be infected as well.
The head of the World Health Organization, Dr Tedros Adhanom Ghebreyesus, said in a post on X that the person who died was in an area where the virus was circulating in animals and where the tiny biting flies were also present.
Investigations into how the person was infected are ongoing, according to the European Centre for Disease Prevention and Control.
So far, the virus has been detected in farm animals in Austria, Belgium, France, Germany, Ireland, Italy, Liechtenstein, Luxembourg, the Netherlands, Portugal, Spain and Switzerland.