MADRID (AP) — A virulent outbreak of equine herpes in eastern Spain has forced European equestrian events to be canceled across the continent.

The International Federation for Equestrian Sports said this week that it canceled events in 10 European countries until March 28. The ban effects upcoming events in Spain, Portugal, Belgium, Italy, Austria, Poland, Netherlands, Germany and Slovakia.

The federation’s general secretary, Sabrina Ibáñez, said an unspecified number of horses have already died from the outbreak.

“This was not an easy decision to block events in mainland Europe, particularly after the major disruption to the FEI Calendar caused by the COVID-19 pandemic,” Ibáñez said. “But this EHV-1 outbreak is probably the most serious we have had in Europe for many decades.”

The outbreak appears to have originated in Valencia, Spain, and has been linked to subsequent outbreaks in three other European countries, the federation said.

The federation is allowing horse jumping shows in Spain, Portugal, Italy and Belgium to go ahead as long as no new horses enter the events and no cases of the virus are detected.