Quarantines of dozens of Thoroughbreds at two New Jersey tracks appear to have contained an outbreak of equine herpesvirus, a potentially deadly virus, officials said. The horses have been isolated at Monmouth Park in Oceanport and the Meadowlands in East Rutherford.

The outbreak was discovered late last month, when 16 horses at Monmouth Park tested positive for the virus. All were quarantined on Oct. 27, along with 80 other horses they shared barns with, said Jeff Beach, spokesman for the state Agriculture Department.

Horses that went to the Meadowlands after Monmouth Park closed were also quarantined, but have not showed signs of illness, he told The Star-Ledger of Newark for Friday’s newspapers.

The racehorses at Monmouth Park will probably be quarantined until early December, track spokesman John Heims said. That would keep them segregated for at least 30 days, well past the typical incubation period of two to 10 days