Long Island duck is a delicacy savored across the country for its mild flavor and tender meat. But its future has been cast into doubt after the last duck farm on the island was quarantined for an outbreak of bird flu.

The farm, Crescent Duck Farm in Aquebogue, N.Y., must now kill its entire flock of almost 100,000 ducks and may go out of business, its owner said in an interview. The highly infectious virus, H5NI avian flu, was detected last week.

The Suffolk County Health Department said that the farm was under quarantine and that state and federal agriculture officials were on site to conduct “depopulating, cleaning and disinfection activities” at the facility, which supplies ducks to many restaurants in New York City and elsewhere. Similar outbreaks have led to the culling of herds and flocks in more than a dozen states.

Doug Corwin, who is part of the fourth generation of his family to operate Crescent Duck Farm, which has been open since 1908, said on Thursday that the future of his business was uncertain.

“I have done this all my life, and we are the last of this industry,” he said. “It is gut-wrenching. You work your whole life for something, and then one day everything is gone.”

Health officials said the risk to humans remained low. “The virus at this point is not transmissible among humans,” Dr. Gregson Pigott, the Suffolk County health commissioner, said in a statement.