Two genetically distinct Shamonda-like viruses are now circulating among European livestock, weeks after researchers identified a previously unrecognized virus in dairy cattle with fever, diarrhea and sharp drops in milk production. Infections have now been reported in six European countries and neighboring Liechtenstein, with researchers investigating whether infection during pregnancy can cause abortions or congenital disease.
The full scale of the outbreak is difficult to quantify. Shamonda-like virus is not subject to uniform mandatory reporting across Europe, and countries are using different surveillance and testing strategies. In Germany’s Baden-Württemberg, 281 cattle operations have tested positive as of Sept. 8, while Switzerland had detected infections in 22 cantons and France had reported confirmed outbreaks in 22 departments by the end of August.
From Unexplained Illness to a New Virus
In June 2026, veterinarians began investigating acute fever, diarrhea, lethargy and marked reductions in milk production in dairy cattle in eastern France. Initial reports came from the Doubs and Ain departments, followed by similar cases elsewhere in the region.
In an investigation of nine initially affected French dairy herds, bulk milk production declined by up to 75%. The proportion of cows with diarrhea ranged from 8% to 100% among herds, and diarrhea generally lasted one to six days. The affected cows generally recovered from the acute disease.
Routine testing did not identify a known cause. Researchers at the École Nationale Vétérinaire de Toulouse and INRAE ultimately used untargeted Nanopore metagenomic sequencing to identify a previously unrecognized Simbu-group orthobunyavirus, provisionally named European Shamonda virus.
Routine testing did not identify a known cause. Researchers at the École Nationale Vétérinaire de Toulouse and INRAE ultimately used untargeted Nanopore metagenomic sequencing to identify a previously unrecognized Simbu-group orthobunyavirus, provisionally named European Shamonda virus.
Reproductive Disease is The Big Unknown
The clinical disease in adult cattle appears to be relatively mild, but the potential consequences of infection during pregnancy are receiving much closer attention.
In the French investigation, researchers tested aborted fetuses from 18 herds. In every herd, an episode of fever and depression in cows had been reported two to four weeks before abortions occurred. Shamonda viral RNA was detected in the placenta and/or fetal organs, including the brain; six fetal brains tested positive. These findings support the possibility of fetal infection associated with abortion.
Swiss authorities have similarly detected Shamonda virus in aborted bovine fetuses. The Swiss Institute of Virology and Immunology said these findings support the possibility that the virus can cross the placenta, while emphasizing that other possible causes of abortion are still being investigated.
French researcher Jean-Luc Guérin told Réussir that researchers need to monitor abortions and possible problems in newborn calves as the first wave of infected pregnancies progresses.
New information from the Netherlands may add to those concerns. Royal GD recently detected the second Shamonda-like variant in a 1-day-old, full-term calf submitted for pathology. The calf showed underdevelopment, limb abnormalities and a star-gazing posture; PCR and sequencing detected the virus in spleen tissue. Royal GD cautioned that it cannot establish whether the virus caused the observed abnormalities.
The finding is notable because historical Shamonda virus infection was associated with congenital abnormalities in calves in Japan, including arthrogryposis, spinal curvature and central nervous system lesions. Researchers concluded that Shamonda virus should be considered a teratogenic virus in ruminants.
Two Variants are Now Circulating
The outbreak also appears to be more genetically complex than initially thought.
Germany’s Friedrich-Loeffler-Institut (FLI) initially identified a Shamonda-related virus, designated SHAV-EU1, that has circulated primarily in southern Germany, Switzerland and France. On Sept. 1, FLI reported a second variant, SHAV-EU2, in cattle from North Rhine-Westphalia, Lower Saxony, Hesse and Thuringia.
The two variants differ across all three genome segments. FLI says the findings point to two separate introduction and spread events, which already overlap in some German states. Both variants have also been detected in the Netherlands.
Orthobunyaviruses have segmented RNA genomes, meaning the L, M and S genome segments can potentially be exchanged when related viruses infect the same host or vector. FLI notes that Germany now has three Simbu-group orthobunyaviruses circulating at the same time: Schmallenberg virus, SHAV-EU1 and SHAV-EU2.
The original French genomic analysis also found that the European virus’s L and M segments clustered with historical Nigerian Shamonda virus, while the S segment showed a different clustering pattern, suggesting mutation or reassortment.
Infection Isn’t Limited to Cattle
The known host range is also expanding.
FLI has confirmed SHAV-EU1 infection in cattle, horses, sheep and goats, while an alpaca in Hesse also tested positive. SHAV-EU2 has so far been detected only in cattle.
The horse findings remain under investigation. One horse in Rhineland-Palatinate developed central nervous system disorders before dying, and FLI detected a high viral load in brain tissue, which it said suggests a possible connection with the clinical signs. Swiss authorities have also detected Shamonda viral material in the brains of two horses with neurologic disease.
The findings do not yet establish that Shamonda caused neurologic disease in the horses, and investigators are continuing to assess the significance of the detections.
The Next Phase of the Outbreak
Researchers are still determining how widely the virus has spread, how efficiently it moves between animals and vectors, and whether the two European variants differ in their clinical effects.
The reproductive effects may take the longest to understand. Viral RNA has been detected in aborted bovine fetuses in France and Switzerland, and the recent detection of SHAV-EU2 in a newborn calf with congenital abnormalities has added another piece to the puzzle. However, researchers have not established how frequently infection during pregnancy leads to abortion, fetal abnormalities or problems at birth.
That uncertainty is likely to diminish as more cattle exposed during the current outbreak reach the end of gestation. European researchers are closely watching the coming calving season for evidence of congenital abnormalities and other reproductive problems.
The outbreak also provides an early look at how quickly an emerging vector-borne virus can move through susceptible livestock populations. With two genetically distinct variants already circulating and multiple animal species infected, researchers will be watching not only where Shamonda-like virus appears next, but also how the virus changes as it establishes itself in Europe.
There is currently no evidence that the European Shamonda-like virus infects people, and European authorities consider the human health risk low. For now, the biggest question is what the virus will mean for European livestock as the first large wave of infections moves from acute disease into its potential reproductive consequences.
