In this series , we answer frequently asked questions about China’s strict zero-tolerance approach to Covid-19 including current entry restrictions, the length of quarantine and which tests travellers have to take. Have a question you want us to tackle? Drop us an email at firstname.lastname@example.org . China has one of the world’s longest Covid-19 quarantine periods as part of its zero-Covid policy , which it has credited for its success in keeping the death toll from the pandemic low within its borders. Under the strategy, community cases and their close contacts are swiftly isolated and populations as large as a few million are repeatedly tested for the coronavirus. It also means that travellers to China must first self-isolate and quarantine for longer than required in most other places. How long is the quarantine in China? The length of quarantine depends on the city and the province , but it is at least 21 days in many places. For example, people entering Beijing must spend 14 days in a hotel, then seven days at home or a hotel, then another seven of “health monitoring”. In Shenzhen, Hongkongers need to spend 14 days in quarantine then seven more being monitored for symptoms. Arrivals can ask to spend the second half of their quarantine period at home. Some provinces have longer periods. Travellers to Shenyang, for instance, have to go through 28 days of quarantine in a hotel and then stay at home for another 28 days of health monitoring. What does science say about how long quarantine should be? The length of quarantine is based on the coronavirus’s incubation period, the time between a person contracting the virus and starting to develop symptoms. The original Covid-19 strain has an incubation period of around six days, while the Alpha variant has a median period of about three days. The more contagious Delta variant has a four-day median incubation period, according to a study of the outbreak in Guangdong from May to June published in the EClinicalMedicine journal. According to the Hong Kong Department of Health, most people with Covid-19 develop symptoms within 14 days of contracting the virus, with five days being the most common. Critics of the 21-day isolation such as epidemiologist Ben Cowling and virologist Jin Dong-Yan of the University of Hong Kong say there is no evidence to support this arrangement. Cowling has repeatedly said an exit test after 10 days of quarantine is sufficient and 14 days of quarantine is “more than enough”. I know of no scientific evidence to justify a 21-day quarantine period. 10 days with an exit test should be enough, 14 days more than enough. Anyone whose suspected exposure in Dorsett WC was only in the third week after their arrival was needlessly put at risk of infection... https://t.co/md7uZC6tHl — Ben Cowling (@bencowling88) August 21, 2021 Jin said the length of quarantine could be shorter for fully vaccinated individuals. “Vaccination can shorten the window of virus shedding,” he said, referring to the phenomenon when the virus leaves the infected person through secretions in the nose and mouth. “The vaccinated people, because they have antibodies, they are actually fighting the virus.” Experts also say the 21-day quarantine at a hotel could raise hygiene concerns , or increase the risk of a person catching the virus at the hotel. Earlier this month, Hong Kong health authorities stepped up measures to curb the transmission of the virus in quarantine hotels after health experts said a man likely caught the more transmissible Delta Plus variant from his neighbour, when both of them opened doors to their room to collect food. Though rarer, some studies have suggested a small proportion of cases could have incubation periods longer than 14 days. In October, a woman tested positive for Covid-19 on the 26th day after arriving in Hong Kong from the United States, with authorities classifying it as an imported case. How long is quarantine in other places? In countries that have chosen to live with Covid-19, there is either no quarantine or the period is short. In Britain, for example, people who are not fully vaccinated are only required to isolate for 10 days, while those who have had the shots can skip quarantine entirely. Quarantine measures vary by state and cities in the US. Travellers to New York state and California, for example, have no restrictions, but local authorities encourage travellers to self-quarantine for seven days if they are not fully vaccinated. Singapore allows fully vaccinated travellers to enter the country without quarantine if they are from certain countries such as Australia, South Korea and the US. Travellers from mainland China, Hong Kong, Macau and Taiwan can also enter unvaccinated and only need to self-isolate while waiting for their Covid-19 test result on arrival. Other countries have stricter measures. Travel to New Zealand without quarantine is only available to those from some Pacific island nations. Other travellers entering the country with a “critical purpose” must be isolated for seven days at a hotel and then at home until they receive their day 9 test results. Travellers to Taiwan need to spend 14 days in quarantine in a hotel or a group quarantine facility. How likely is China to shorten its quarantine period soon? Local governments in China have not announced plans to shorten their quarantine periods. Some, such as Guangzhou, have made isolation measures stricter because of an outbreak that started in October. The Chinese government has also not said when it will relax border restrictions. But respiratory diseases specialist Zhong Nanshan has said China could reopen if the Covid-19 case fatality rate – the proportion of those infected who die from the disease – is controlled at 0.1 per cent and an infected person infects only an average of 1 to 1.5 people. The global case fatality rate fell to around 2 per cent in November, according to data from Johns Hopkins University, while countries with high vaccination rates have a much lower case fatality rate. The case fatality rate of Delta variants for vaccinated people in Britain, for example, is between 0.14 to 0.18 per cent, according to Jin . Some travellers from Hong Kong, however, are expected to be able to enter mainland China quarantine-free from December, although there will be a limited quota of a few hundred people per day to start with.