Officials at Pimlico Race Course in Maryland have isolated five horses in the detention barn and put a "hold order" on barn 5 while they determine whether a horse stabled in the barn, who was euthanized earlier this week, was infected with equine herpesvirus. Equine herpesvirus-1 (also known as "rhino") causes upper respiratory infection and can also cause neurological disease, which five other horses in barn 5 have experienced, according to a statement from the Maryland Jockey Club. The NJC reported the "hold order" affects the barn that houses horses trained by William Christmas, Charles Frock, Robert Gamber, Hassan Elamri and David Mohan. Horses conditioned by those trainers are not allowed to race until further notice, according to the statement. Beginning Saturday, the 40 horses remaining in the barn will be allowed to train from 10-11 a.m. The other 500 horses based at Pimlico will train from 5:30-9:30 a.m. The Pimlico spring meet begins in mid-April, with live racing currently being conducted at Pimlico's sister track, Laurel Park. "The hold order, which restricts the movement of horses to and from the affected barn, is a precautionary measure to prevent any possible spread of illness among horses while we wait for diagnostic test results," said Maryland state veterinarian Guy Hohenhaus. "We are working with track management to keep the healthy horses in training while protecting the health of all other horses at the facility. They are athletes and need to stay in their routine as long as the investigation permits." According to the MJC, the Maryland Department of Agriculture placed an initial "Investigational Animal Hold Order" on Jan. 5. and that, even before that time, Maryland Jockey Club officials "ensured that no non-resident horses came in contact with the affected horses or the barn in which they are housed. Based on clinical signs, there is no reason to believe that there is any human health risk. "There is currently no known method to reliably prevent the neurologic form of EHV-1 infection. It is recommended to maintain appropriate vaccination procedures in an attempt to reduce the incidence of the respiratory form of EHV-1 infection, which may help prevent the neurologic form. Transmission of the virus can occur via coughing or sneezing over a distance of up to 35 feet as well as by direct contact with infected horses, feed and equipment. EHV-1 cases were reported at Turfway Park, Churchill Downs, Prairie Meadows, Calder Race Course and The Meadows in 2005. Maryland Jockey Club racing secretary Georganne Hale and Dr. David Zipf, the veterinarian for the Maryland Racing Commission were to be available to the press at 3:00 in the Laurel Park racing office Friday afternoon, the statement said, adding that "the press will not be allowed into the stable area at Pimlico until further notice."