An apprentice jockey has tested positive for coronavirus, the BHA confirmed on Sunday.
The rider in question, who has not been named, is the first to have been reported to have tested positive since racing resumed on June 1 following the shutdown.
The jockey has not ridden "for a few weeks" and has not been racing since they were found to have the virus.
A BHA spokesman said: "Having been notified that an apprentice jockey had tested positive for coronavirus, the BHA has worked with the health protection agency, PJA, the jockey and their yard to assist their employer in following government guidance and managing the jockey's recent close contacts.
"A handful of people have been identified and asked to self-isolate for 14 days as a result. Further tests taken by close contacts have not returned any further positive results.
"The jockey in question has not taken a ride for a few weeks, though attended a recent race meeting as a member of stable staff, prior to showing any symptoms and before their positive test.
"It remains important that everyone involved in the sport follows government and racing guidelines and protocols around social distancing and environment hygiene at all times."
The coronavirus pandemic caused racing to be shut down from mid-March and since resumption behind closed doors all riders, and other key personnel allowed on course, have been subject to strict protocols.
They must complete health questionnaires and undergo temperature checks as a condition of attendance.
While this is the first case of a jockey confirmed as positive in Britain, there have been cases among riders in other prominent racing countries, including the US.
Racing was suspended at Del Mar in California last month after 15 jockeys tested positive.