TAIPEI, Taiwan >> Closed schools and restaurants offering takeout only. Lines around the block at testing sites. Politicians on television urging the public to stay calm.

If the scenes around Taiwan this week have a distinctly early pandemic feel, it is because the coronavirus is only now washing up on the island’s shores in force. A crush of new infections has brought a swift end to the COVID-free normality that residents had been enjoying for more than a year.

By shutting its borders early and requiring two-week quarantines of nearly everyone who arrives from overseas, Taiwan had been managing to keep life on the island mostly unfettered. But all that changed after enough infections slipped past those high walls to cause community outbreaks.

For most of the past week, the government has ordered residents to stay home whenever possible and to wear masks outdoors, though it has not declared a total lockdown. Local authorities are ramping up rapid testing, though some health experts worry that too few tests are being done to stay ahead of the virus’s spread.

Taiwan’s latest numbers — between 200 and 350 new infections a day for the past several days, and a few deaths — are still low by the standards of the hardest-hit countries. On Thursday, it reported 286 new local infections. But the uptick has jolted a population that, until last Saturday, had recorded only 1,290 COVID-19 cases and 12 deaths during the entire pandemic.

Adding to the concern: Only around 1% of the island’s 23.5 million residents have been vaccinated against the virus so far.

“This day was bound to come sooner or later,” said Daniel Fu-chang Tsai, a professor at the National Taiwan University College of Medicine. The slow pace of immunizations combined with more transmissible variants to create a perfect “window,” Tsai said, for the island to experience a flare-up.

It did not help, he said, that more people had been leaving their masks at home and abandoning social distancing.

“It’s like Swiss cheese,” Tsai said. “There were a few holes in the front and a big hole in the back. But this time, the blade happened to pierce straight through.”

Before this month, Taiwan had spent the bulk of the pandemic happily shielded from its worst ravages.

Eight months passed last year without a single case of community transmission until an infection in December snapped the streak. Even after that, local infections cropped up only sporadically for months.

Then the tide shifted — gradually, then suddenly.

On April 14, the government began allowing crew members for Taiwanese airlines to quarantine at home for just three days after arriving on long-haul flights, down from the previous requirement of five days.

A week later, China Airlines, Taiwan’s flag carrier, told the government that one of its pilots had tested positive in Australia. Health officials began expanding testing for airline workers. Soon, more pilots and their family members were testing positive, as were employees at a quarantine hotel.

On May 10, a pilot who had been in the United States tested positive after completing his three-day quarantine, but not before he had visited a pub and a restaurant in Taipei.

All China Airlines crew members were ordered into rolling 14-day home quarantines. But it was probably too late. A cluster of infections began to emerge among workers and patrons at so-called hostess bars in Taipei’s Wanhua District.

By the end of the week, daily case numbers had soared into the triple digits.

So far, the search for new infections has been concentrated in the populous cities of Taipei and New Taipei, where more than 1,600 people can receive rapid testing each day. Hospitals are also providing slower testing services.

Dr. Chiang Kuan-yu, 37, a physician at Taipei City Hospital, went to Wanhua District on Monday to help run a testing site there. He said there had been big crowds over the weekend, when the case numbers first started to rise. Some people had to wait an extra day to get tested.

“Now there are more resources for testing, so we can keep up better,” Chiang said.

Officials are trying to use test centers efficiently by testing only those who are showing symptoms or may have come in contact with infected people.

Chen Shih-chung, Taiwan’s health minister and head of its Central Epidemic Command Center, has urged those with no COVID-19 symptoms and no history of contact to not even come to testing sites, lest they become infected there.

“This only will slow down our search for possible spreaders,” Chen said in a news briefing. “Don’t go there thinking, ‘Oh, maybe I’m infected, maybe it’s best that I get tested.’ You absolutely must not come.”

But Dr. Wang Jen-hsien, an infectious disease specialist at China Medical University Hospital in the central Taiwanese city of Taichung, called this an excessively “frugal” approach. He urged the government to consider locking down Wanhua District and testing all residents.

“Before, Taiwan was a safe society. If you tested randomly back then, of course you would endanger public health,” Wang said. “But now if it’s a high-risk zone, then you can’t do things this way. Your way of thinking has to change.”

Taiwan received its first doses of the AstraZeneca vaccine in early March, and it has since been gradually immunizing health workers and other priority groups. Officials say doses of the Moderna vaccine will arrive soon. Several Taiwanese companies are also developing vaccines.

Taiwanese authorities began working with domestic vaccine producers in January 2020, after the coronavirus’s genetic sequence was made available and before the Chinese city of Wuhan went into lockdown.

“Taiwan got started extremely early,” said Dr. Ho Mei-shang, a research fellow at the Institute of Biomedical Sciences at Academia Sinica in Taipei who was involved with the government’s vaccine efforts. “We said at the time, ‘Whatever the vaccine ends up being, we want make it ourselves as quickly as possible.’”

But Taiwan’s insistence on developing and producing its own immunizations may have made officials less quick to snap up overseas vaccines when those started becoming available, Ho said.

“And then,” she said, “by the beginning of this year, when the pandemic was so severe in so many countries, we just said we’ll wait a little.”

Even after the AstraZeneca vaccine first became available in Taiwan, the low case count meant many people felt no urgent need to get immunized.

Still, Ho said she was heartened to see how quickly people in Taiwan were adjusting to the new restrictions on daily life, even after such a carefree past year.

Recently, she went for a run at 10 p.m. and forgot to wear her mask at first. But she noticed that even at that hour, everyone else who was out walking and exercising was masked up.

“This is a state of affairs,” she said, “that really sets Taiwan apart.”

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