Three weeks before the Winter Olympics, Beijing says it has an Omicron infection. A case of the highly contagious Omicron variant of COVID-19 was found in Beijing on Saturday, just a few weeks before the city is set to host the Winter Olympics.

Omicron’s arrival comes at the same time as China’s capital has been put on high alert for the arrival of international athletes from all over the world. First, the Omicron variant spread to Tianjin, a port city near Beijing, less than a week ago. It has since spread to other cities in China.

People at a news conference said the person had a low fever on Friday and took a voluntary test. The Omicron case was first found on Saturday morning.

After the positive test, municipal health officials sealed off the patient’s home and the office building where he or she works and ordered more than 2,000 tests for people who live or work near those places, too.

Officials had a long list of places the person had been to in the last two weeks, including shopping malls and restaurants. A new ski resort that isn’t used for the Olympics was also on the list. There were rules for quarantine that people who went thru any of those places with a patient were told about by officials. People who did not follow them could be found to be in violation of the law, they said.

Covid controls in the capital depend on your help, says Pang Xinghuo, deputy director of the city’s Center for Disease Control and Prevention. In her speech, Ms. Pang said that the city was at risk of both cases that came from outside and those that came from inside.

Beijing’s response is in line with China’s “Covid-zero” policy, which tries to get rid of outbreaks as soon as they start up anywhere. In the last two years, cities all over China have used the same strategy to stop outbreaks: lockdowns and mass testing.

Officials in Xi’an, a city in central China, have kept the city’s 13 million residents inside their homes for weeks as they try to figure out how to deal with a lot of crimes. People in Xi’an said that the wave of infections there was coming to an end on Saturday, so some parts of the city began to be freed from rules.

Authorities in Tianjin started a mass testing campaign last weekend after two cases of the Omicron variant were found in the city. The city has a population of over 14 million people. At the end of the week, Tianjin said it had found 203 cases that had been spread locally. It didn’t say how many of those cases were of the Omicron variant.

As the Omicron variant of the virus spreads around the world, there is more pressure on Beijing officials to keep the city safe from foreigners who might bring the virus with them from other countries.

Beijing has set up a so-called “closed loop” for the Winter Games participants to work in. This means that they won’t be able to see the rest of the city, and they won’t be able to go anywhere else.

Authorities have told people not to go outside during the Lunar New Year holidays, which start a few days before the Winter Games start on Feb. 4. It has also made it more difficult for people from other parts of China to get into the city. One of the city’s official newspapers said this week thatany city that has even one case of COVID-19 will not be able to sell plane tickets to the capital.

Officials say they want to keep illnesses brought in from other countries from getting worse and spreading to people at home.

Officials in Beijing say that the city’s hundreds of medical clinics are closely monitoring infections, and a team of more than 3,000 people led by epidemiologists has been called in to find people who might have been in contact with the person who died.