Neighborhoods under strict lockdown. Thousands quarantined. Millions tested in mere days. Overseas arrivals locked up for weeks and sometimes months.

China has followed variations of that formula for dealing with the coronavirus for more than a year — and a new outbreak suggests that they could be part of Chinese life for some time to come.

China appeared to get the coronavirus under control nearly a year ago. But hundreds of millions of Chinese people remain unvaccinated. New variants of the coronavirus have appeared, and questions remain about whether China’s self-made vaccines can stop them.

The latest cases have been found in Guangzhou, the capital of the southern province of Guangdong. The authorities have blamed the Delta variant, which has caused widespread loss of life in India.

The city tested practically its entire population of 18.7 million between Sunday and Tuesday, some of them for the second time. It has also put neighborhoods with a total of more than 180,000 residents into total lockdowns, with practically no one allowed out except for medical testing.

The early infections appear to have jumped from person to person at a cluster of eateries. Each infected person has infected more people than in any previous outbreak that China has confronted, Zhang Zhoubin, deputy director of the Guangzhou Center for Disease Control, said at a news conference.

“The epidemic faced by Guangzhou this time is an unprecedented opponent, and it requires more resolute and decisive measures to deal with it,” he said.

Test facilities in Guangzhou have been operating around the clock. Lines are long. Residents wake early to try to beat the rush, but still find delays.

Mandy Li, a longtime resident of the city’s Liwan District, where most of the infections have occurred, said she set her alarm clock for 3:30 a.m. She still had to wait an hour.

“In the queue, there was a family of three,” she said. “Some woke their kids to line up, and some had strollers. But everyone was cooperative and quiet, as we know some volunteers and medical workers worked very hard and they’ve been there all this time without rest.”

China’s approach has evolved since the coronavirus first emerged when Beijing initially put harsh restrictions on hundreds of millions of people. Today its lockdowns are focused on neighborhoods rather than cities or provinces. China has made vaccination the centerpiece of its strategy.

Still, many of the core tenets remain for a huge and densely populated country: vast testing, strict limits on movement, and intense scrutiny of arrivals from other countries.

Foreign businesses have worried that those limits on international travelers could snarl their plans. A European Union Chamber of Commerce survey released this week found that three-quarters of member companies said they had been adversely affected by travel restrictions, usually by hindering them from bringing in key engineers or executives.

Beijing has demanded that travelers from dozens of countries spend two weeks in employer-supervised quarantine even before flying to China. Once there, travelers must spend at least two weeks and sometimes three or longer in government-supervised quarantine, even if they are fully vaccinated. Rounds of tests can turn up a possibly false positive, leading to more tests and additional days or weeks in isolation.

A German national who flew into Shanghai last month said that he had been sent to a hospital isolation room for three days because he tested positive for antibodies, which he attributed to taking a second vaccine dose 16 days earlier.

Nurses took his blood twice a day and performed six throat swabs, four nasal swabs, and two anal swabs daily, said the German, who insisted on anonymity to avoid offending the authorities. The hospital room had no towels, no toilet paper, and no television, and the bed was a steel plate with a thin mat, he said.

The German said that, after consistently testing negative for the virus, he was allowed to spend the remaining 11 days of isolation in a government-supervised quarantine center.

Many businesses expect that China may retain stringent travel restrictions through February when Beijing will host the Winter Olympics, and possibly through autumn of next year when the Chinese Communist Party will hold its party congress.

Many foreigners in China face a choice: If they leave to visit spouses, children, and other family members elsewhere, they may be unable to re-enter the country later because of the pandemic restrictions.

“There is absolutely a growing fatigue for a lot of the foreigners who are here,” said Jacob Gunter, senior policy and communications manager at the European Union Chamber of Commerce in China.