BBC
Beijing says it's taken all necessary coronavirus safety measures for the 2022 Winter Olympics.
Positive cases have been reported at the Games, and there've been complaints from some athletes about how these have been handled.
So what safety measures are in place, and how successful has China's policy of "zero Covid" been?
What are the isolation rules at the Games?
Anyone testing positive after arrival is put into isolation and only allowed to compete after getting two consecutive negative tests taken 24 hours apart.
Those who have symptoms will be taken to a designated hospital and those who are asymptomatic will stay in an isolation facility. They're not allowed to go outside, but can request training equipment for their room if it's available.
Athletes competing in the Games are tested daily
There's also been some confusion over testing, with one competitor, Polish athlete Natalia Maliszewska, claiming that conflicting results meant
she was allowed to compete in one race and then sent straight back into isolation.
And some athletes are unhappy about the isolation facilities they've been sent to after testing positive.
What other measures are in place?
Foreign spectators are barred and tickets are not on sale to the general public.
Groups of local spectators are being "invited" to events and will have to observe strict Covid prevention measures "before, during and after watching the Games."
High-speed trains will run within a closed transport system for the Olympics
And people are advised not to travel into the capital, Beijing, from other parts of China.
It is also keeping the media, athletes and observers in distinct bubbles, with the rules saying anyone entering these bubbles must be fully vaccinated or spend 21 days in quarantine.
Overseas participants will enter a bubble upon arrival in China, and remain in it until they leave the country.
Local support workers, including volunteers, cooks and drivers, will also be part of a sealed bubble. They'll have no physical contact with the outside world, even with their own families.
This system applies not just to housing, hospitals and locations meant to serve the Olympics, but also transport links. There are closed-loop airports and high-speed rail systems (most major venues are outside Beijing).
Local traffic authorities have even advised the public to "avoid contact" if they have a road accident with a vehicle carrying Olympic personnel.
What did China do earlier in the pandemic?
Travel to and from China has been severely limited, and there have been restrictions on internal movement for some two years now.
Any travellers from abroad who have permission to enter China are screened on arrival and sent to government-designated hotels for a mandatory quarantine of at least two weeks.
All international passengers must have temperature checks before disembarking
In most cities, this is followed by a further seven days of hotel or home quarantine, and then a seven-day monitoring period when social mixing is prohibited and regular reporting to local health officials is required.
China has stopped issuing and renewing passports for "non-urgent purposes" to its own citizens both at home and abroad, to further minimise international travel.
There are also strict controls on moving between China's cities (and sometimes between individual neighbourhoods) with further mandatory periods of self-isolation for those permitted to travel.
China has also put some cities into lockdown when cases have been detected.
Residents of Xi'an gather to collect essentials after the city was locked down
During these, people are only allowed to leave for "urgent matters", such as going to hospital. Surveillance by the police and local volunteers is also being stepped up, with harsh penalties for anyone breaking the rules.
Residents can be evicted from their homes at short notice and sent to quarantine facilities if infections are detected during a mass testing campaign. All non-essential businesses are shut, apart from food shops and some other essential suppliers.
Schools are closed and public transport is suspended, with almost all vehicle movement banned.
How successful has 'zero Covid' been?
On the face of it, China has had remarkable success containing the pandemic.
Since the end of 2019, China has reported just over 4,600 deaths (according to Our World in Data). In the United States, more than 830,000 have died and in the UK, just over 150,000.
Per million people, that's around three deaths in China, compared with 2,500 in the US and 2,190 in the UK.
Reported infections in China have also been very low, rarely rising above 150 a day across the country throughout the pandemic.
Concerns have been expressed about the accuracy of the official data, but it seems clear that both infection and death rates have been low when compared with other countries. The National Health Commission in China says 85% of its population is now fully vaccinated.
Despite this, China is almost alone in adhering to a zero-Covid policy regardless of the cost to personal freedoms and to the economy.
