BEIJING • Leave your partner and children behind. Quarantine for up to a month. Get inoculated with a Covid-19 vaccine from China - if you can find one. And prepare yourself for an anal swab.

For the past year, people trying to go to China have run into some of the world's most formidable barriers to entry.

To stop the coronavirus, China bans tourists and short-term business travellers outright, and it sets tough standards for all other foreigners, even those who have lived there for years.

The restrictions have hampered the operations of many companies, separated families and upended the lives of thousands of international students. Global companies say their ranks of foreign workers in the country have dwindled sharply.

At a time of strained tensions with the United States and other countries, China is keeping itself safe from the pandemic.

At the same time, it risks further isolating its economy, the world's second-largest, at a moment when its major trade partners are emerging from their own slumps.

"When it comes to measures that draconian, you are going to disenfranchise people who are big China fans and are not allowed to return to the country they have made their home," said Mr Alexander Style, the British owner of a Shanghai-based company that makes electric vehicle (EV) parts for export, who has been forced to relocate with his family to New Jersey.

Other countries have their own travel restrictions, though few are as tight. The US, for example, bans foreigners travelling directly from China unless they are green card holders or certain immediate family members of American citizens. It also bans foreigners leaving from Europe, as well as Brazil and some other countries.

Australia lets in just a few hundred of its citizens and permanent residents each day, while Japan has barred the entry of foreign workers and students since late December.

In China, officials regard travel limits as crucial to their success in containing the virus. Since the outbreak started, China has reported more than 101,000 Covid-19 cases. Although questions have been raised about the accuracy of the numbers, they are far lower than those in the US, where 29.8 million have tested positive for the virus.

China was the only major economy to grow last year. It knows businesses will find a way to keep their Chinese operations running, with or without expatriates, and it is betting that they will come back when the pandemic eases.

At the same time, China's border restrictions highlight the inadequacies of its vaccine roll-out, which has been slow compared with those of the US, Britain and other countries.

Foreign executives think China is likely to be one of the last countries in the world to fully reopen, perhaps as late as next year, after the Beijing Winter Olympics in February. China's restrictions will mean significant delays in building large factories or winning sales orders, according to business groups.

In recent days, Chinese embassies in at least 50 countries have said foreigners wanting to enter China could avoid some visa paperwork by taking a Chinese-made Covid-19 vaccine.

The government has presented the rule as an easing of its visa application procedures. But it does not help travellers from countries like the US where Chinese vaccines are not available.

"It's kind of a Catch-22," said Mr Jeff Jolly, who has been stuck in the US since July after leaving Shanghai, where he runs a language training centre and academic consultancy.

In a statement, China's Foreign Ministry said: "We believe this is a meaningful exploration of facilitating international travel once mass vaccination has been achieved." As deadlier and more infectious virus variants appeared in other countries in recent months, China introduced onerous new requirements.

At the end of last year, it essentially stopped allowing anyone to bring a spouse or child into the country. Since January, travellers arriving in Beijing from countries with severe outbreaks have had to endure weekly anal swab tests while in quarantine, with faecal material tested for traces of the virus. The measure prompted complaints from the US and Japan.

Last month, the government announced that foreign and Chinese travellers coming from more than two dozen countries would have to do two weeks of employer-supervised quarantine overseas before they were even allowed to fly to China. Then, after landing, they were expected to spend two more weeks at a government-managed quarantine facility.

The number of foreign business managers in China has slumped. A survey of 191 businesses in southern China by the US Chamber of Commerce found that 70 per cent had fewer than five expatriate employees in China at the end of last year, compared with 33 per cent a year earlier. The proportion of companies with no expatriates had surged to 28 per cent from 9 per cent a year earlier.

Mr Style, the owner of the EV parts company, said the Chinese visa process now favoured big companies that contribute a great deal of tax revenue, not start-ups like his business. He said he had settled down in the US - his wife is American - and did not plan to return to China any time soon.

The Foreign Ministry said China's re-entry policy "treats all foreign personnel equally, and there is no so-called differential treatment".

China's restrictions have been compounded by decisions on visas and entry requirements that can seem arbitrary to those trying to return.

Mr Glyn Wise, who had been teaching English literature at an international school in Shanghai, was able to get a work visa from the Chinese Embassy in London in October. But the agency that helped prepare his application told him later that Chinese border officials would not acknowledge the visa.

"A lot of the times they would change the rules about who they were accepting," Mr Wise said. He said he was looking for job opportunities outside China.

But many others are still hopeful, and some have organised campaigns on social media to draw attention to their plight.

Nearly 13,000 international students signed an online petition urging Beijing to allow them to return to China, while others launched a Twitter campaign called #TakeUsBackToChina.

Mr Amanuel Tafese, an Ethiopian student enrolled at a university in Chengdu, said he had tried taking his lessons online since being shut out of the country early last year. But he had to rent space to do so, because there is no electricity or Internet access at his family's home 450km from the capital, Addis Ababa.

Mr Tafese said he cannot find a job because he has no degree, and is relying on his father's small income to support himself. "All this made me depressed," he wrote in an e-mail.

NYTIMES