French health authorities have confirmed the first documented human infection with the Shamonda virus, an insect-borne disease previously known to affect livestock, after a severely immunocompromised patient died at a hospice in Lyon in early October.
The French Ministries of Health and Agriculture announced the development on Thursday, describing the case as exceptional because Shamonda had never previously been detected in humans despite circulating among animals in Africa and Asia for decades.
According to the authorities, preliminary investigations indicate that the neurological complications suffered by the patient before death were “very likely” linked to the Shamonda virus infection.
However, they stressed that clinical, biological and epidemiological investigations are continuing.
The authorities also said there is currently no identified health risk to the general population, noting that the infection occurred in a severely immunocompromised patient who was already being treated for a serious medical condition.
“Despite circulating in Africa and Asia for several decades, the Shamonda virus has never previously been detected in humans,” the ministries said, describing the case as an exceptional occurrence.
The leading hypothesis is that the patient was infected through the bite of a Culicoides midge in eastern France, where Shamonda had been circulating among animals during the spring and summer.
Shamonda is an Orthobunyavirus belonging to the Simbu serogroup. It is primarily transmitted among animals by biting midges and mainly affects cattle, although infections have also been detected in sheep, goats, horses and alpacas.
The patient’s infection was discovered following investigations into the neurological complications that developed before death.
French authorities said the preliminary evidence strongly suggested a link between the complications and Shamonda infection, but cautioned that further investigations are required to establish the full clinical and epidemiological circumstances.
The World Health Organisation (WHO) and the European Centre for Disease Prevention and Control (ECDC) have been notified of the case.
The first known human infection comes just months after Shamonda was detected in Europe for the first time.
The virus was confirmed on the continent in late July following genomic investigations involving sick cattle in southern Germany, Switzerland and eastern France.
It has since been detected in 14 European countries, according to French animal-health surveillance information.
The affected countries include France, Germany, Austria, Belgium, Ireland, Italy, Liechtenstein, Luxembourg, the Netherlands, Portugal, Slovenia, Spain, Switzerland and the United Kingdom’s Jersey.
Cattle are considered the principal hosts, with infected animals showing symptoms including fever, acute diarrhoea, lethargy and a sharp decline in milk production.
Animal-health authorities have also reported reproductive complications, including abortions, while infection during pregnancy has raised concerns about possible congenital abnormalities.
The virus is not considered fatal in cattle, although authorities continue to investigate its wider impact on livestock and the characteristics of the variants circulating in Europe.
Rising Temperatures Under Investigation
Scientists are also examining whether unusually high temperatures in Europe may have contributed to the virus’s emergence and spread.
Martin Beer, head of diagnostic virology at Germany’s Friedrich Loeffler Institute, previously said exceptionally warm conditions could have been one of several factors that enabled the virus to reach Europe and spread among livestock.
He cautioned, however, that temperature was only a possible contributing factor and that several environmental and epidemiological factors could have been involved.
Because Shamonda is transmitted by biting midges, changes in temperature and environmental conditions may influence the distribution and activity of its insect vectors.
Shamonda virus has a significant Nigerian connection, having first been identified in cattle in Nigeria in 1965.
It has since been reported sporadically among animals in other parts of Africa and Asia, including Japan, but there had been no documented human infection until the French case.
The virus is genetically related to other members of the Simbu serogroup, including Schmallenberg virus, another insect-borne disease affecting livestock.
There is currently no specific vaccine or antiviral treatment for Shamonda virus.
The World Organisation for Animal Health (WOAH) has emphasised the importance of surveillance, early detection and information-sharing between animal and human health authorities as scientists work to understand the virus and its implications.
For now, French authorities maintain that the Lyon case does not constitute evidence of a wider public health threat.
