NEW ORLEANS - Thoroughbreds raced around the track at the New Orleans Fair Grounds Friday night as crowds cheered them on hoping for a big win. But while everything seemed well on the outside, the reality is something different these days.

The track is under a state-ordered quarantine, mandated after more than a dozen horses tested positive for the equine herpes virus.

"What we're trying to do is to make sure no horses come in or go out until we have the virus contained and controlled," said Mike Strain, the state agriculture and forestry commissioner.

As of Friday, 39 horses at the Fair Grounds tested positive for the highly-infectious disease and were placed in isolation. Another horse with the virus was euthanized last month.

Humans cannot contract the disease.

"What we don't want is for horses to leave the Fair Grounds and go to training centers or other tracks and possibly spread this disease," Strain said. "If this gets widespread throughout Louisiana then our problems will grow exponentially."

The quarantine is costing horse owners a lot of money.

Orleans Parish Clerk of Criminal Court Arthur Morrell has four horses at the Fair Grounds.

He said that since horses can't ship in or out, those who own them are missing opportunities to run at other race tracks.

“When they have a horse that can't run, then you are just paying money out and they have no chance of anything coming in,” Morrell said. “You can prep a horse for a race, and if a horse has tested positive in your barn, you may have to scratch your horse and all the money that you put in to preparing that horse is lost.”

Morrell added that some horses may miss an opportunity to run in the most prestigious race of the year because of the quarantine.

“You have horses that are here that are … potential candidates for the Kentucky Derby,” Morrell said. “If for some reason this quarantine lasts beyond the time they need to be able to enter in that Kentucky Derby, they can't enter their horse.”

Fair Grounds Senior Director of Operations Brad Bryant said the track was showing significant gains year over year in handle and field sizes – the amount of money bet on a race and the number of horses in a race, respectively -- before the discovery of the virus two weeks ago.

“We were on a roll leading up to when this broke out," Bryant said. “We expect to get this handled, keep the quarantine in place until we can get out of it. Until then, it's business as usual.”

Bryant maintained that less than 5 percent of the horses housed at the track are affected by the illness. He admitted it's too soon to know how long the Fair Grounds will be on lock down.

“We've got a lot of good horses on the grounds,” Bryant said. “We're open and we're hoping that (the problem) is going to take care of itself.”

The equine herpes virus has been detected in six of the Fair Grounds’ 49 barns.

“There are going to be some challenges over the next 45 days as we work through this, but we're hoping that by testing in 14 day intervals, we can get more of the barns released,” Stain said.

The virus was last detected at the Fair Grounds in 2008.