TAIPEI, Taiwan ­— Authorities in Taiwan, which has led the world in covid-19 containment, said Tuesday they would roll back foreign flights and tighten quarantine requirements for crew members after identifying the first locally transmitted coronavirus case since April, stemming from a cargo pilot who flew routes abroad, including to the United States.

The reports of a single new case and its particulars — the pilot, a New Zealander, was said to have been coughing during his last flight but did not wear a mask at all times — immediately sparked public consternation as they snapped the island’s record without a domestic transmission. The 253-day streak had been a point of pride for Taiwan’s 23 million people and its leaders.

Taiwanese officials said Tuesday they would cut passenger flights from London by half beginning Wednesday because they feared the possibility of importing the new viral variant that has recently spread in Britain. Taiwanese citizens, meanwhile, fumed about the lax controls surrounding pilots from abroad and whether a new cluster of cases could derail public New Year’s celebrations.

The Taiwanese government also fined the pilot the maximum under the law, about $10,000 for failing to report his symptoms and contacts as it issued stern warnings about personal accountability.

“Wear your masks well and let’s not fumble this now, especially when we’re in a period with a mutation that’s transmitting fast,” Taiwanese Health Minister Chen Shih-chung said Tuesday, showing a flash of frustration. “We need to have stricter controls for pilots. Our measures weren’t actually being implemented.”

Recent cases in Taiwan, China, Australia and elsewhere have underscored how easy it is for the coronavirus to regain a foothold even in places where public health authorities had contained it through careful quarantine, isolation and contact-tracing policies. Authorities have turned their attention recently to flight crew members, who are sometimes afforded more relaxed quarantine requirements compared to passengers because they need to fly so frequently.

In Taiwan, for instance, arriving pilots are quarantined for three days and cabin crew members for five. New regulations — potentially upping the quarantine period to the usual 14 days for most travelers — would be announced later this week, Chen pledged. “We’re definitely going in the direction of stricter,” he said.

At the urging of public health experts, Australian agencies this month imposed strict quarantines in hotels monitored by police after a dozen Chilean crew members were caught partying during a layover in Sydney — and made headlines.

In the most recent case of domestic transmission in Taiwan, authorities believe the New Zealander pilot, who is normally based in Taiwan, returned from a trip to the United States on Dec. 4, and then met a friend, a woman who worked at the Quanta Computer hardware maker, several days later, between Dec. 8 and 12. The pilot did not report his meeting the woman when asked, and it was discovered only when contact tracers “investigated his movements,” Taiwan’s epidemic control center said without giving details about its tracking methodology.

The pilot was fined about $10,000 for “covering up symptoms, contacts, and places visited while sick,” the spokeswoman for President Tsai Ing-wen said on Twitter late Tuesday. “The mood is alert, serious. Personal accountability is key.”

Taiwanese officials, including Premier Su Tseng-chang, urged citizens on Tuesday to consider staying home during New Year’s celebrations but stopped short of canceling any public events.

“You can get better angles from television,” Su said, referring to annual fireworks show at the Taipei 101 skyscraper.

Officials earlier this month called on the country to not forget to wear masks or grow complacent heading into the holiday period. Masks are almost never worn in Taiwan’s packed restaurants, bars and nightclubs, and rules are unevenly enforced in busy shopping centers.

Since the start of the pandemic, Taiwan has reported 771 cases and seven deaths.

Lily Kuo in Taipei and Lyric Li in Beijing contributed to this report.