As of January 25, the disease has been detected in cattle, sheep and goats in the Netherlands, Germany, Belgium and, more recently, in sheep in the United Kingdom.
The disease causes transient clinical signs in adult cattle - fever, diarrhoea, reduced milk yield - and congenital malformation in newborn animals.
The virus is primarily transmitted via biting midges.
While no official word has been given on the risk to horses, the closely related Akabane virus, which is not found in Europe, is not known to cause any disease in horses, although animals have shown an antibody response to the virus.
The European Centre for Disease Prevention and Control said investigations are ongoing in the affected countries and animal surveillance has been strengthened in neighbouring countries.
The centre said genetically closely related Orthobunyaviruses have not been shown to cause disease in humans.
"Therefore, disease in humans is unlikely but cannot be excluded at this stage.
"The animal and human health services are closely collaborating to ensure rapid detection of any change in the epidemiology in animals and humans, particularly in people with close contacts with animals," it said.
The health of farmers and veterinarians in close contact with potentially infected animals should be carefully monitored, authorities said.
The European Standing Committee on the Food Chain and Animal Health said in a statement that although the congenital malformation in newborn animals have been detected recently and are still being detected, they are most likely caused by transmission of virus by insect vectors that occurred in summer and early autumn, during pregnancy.
It noted that information on the Schmallenberg virus is still fragmented and mostly extrapolated from data available on genetically similar viruses in the Orthobunyaviridae genus (Simbu serogroup, such as the Akabane virus).
Akabane virus is also characterised by foetal damage. Between 1972 and 1975, this virus resulted in the birth of more than 42,000 abnormal calves in Japan, according to a fact sheet issued by the Center for Food Security and Public Health at Iowa State University.
"Symptomatic infections have been seen only in cattle, sheep and goats. Wild ruminants can be infected with Akabane virus; congenital defects might occur in these species, but there are no reported cases in the literature.
"Antibodies to Akabane virus have also been found in horses, donkeys, buffalo, deer and camels. One isolate (NT-14) was reported to be widespread among pigs in Taiwan. Mice and hamsters can be infected experimentally," it said.