Beijing, China (AFP) — The number of COVID-19 cases in China reached its highest level since March 2020 on Monday, as Beijing races to smother outbreaks just three weeks before hosting the Winter Olympics.

With growing fears about the highly-transmissible Omicron strain challenging China’s stringent approach to virus control, a senior health official told residents of the capital to “avoid buying goods from overseas” after saying a local case could have been infected by international post.

China, where the virus first emerged in late 2019, has stuck to a strict policy of targeting zero COVID cases even as the rest of the world has reopened.

But its approach has come under sustained pressure in recent weeks with multiple clusters in key cities just as the Games are about to get under way in Beijing.

On Monday there were 223 more cases reported, including another 80 in the virus-hit port city of Tianjin, and nine more — including cases of the highly transmissible Omicron variant — in the southern manufacturing hub of Guangdong.

Athletes and officials have already started to land in the capital ahead of the Games, immediately entering a tightly controlled bubble separating them from the rest of the population.

But after a local Omicron case was detected in Beijing over the weekend, authorities also tightened regulations for arrivals from elsewhere in China.

The city is now demanding a negative test before travel and a follow-up test after entering, with residents urged not to leave the capital for the upcoming Lunar New Year holiday.

Some tourist sites have also been closed.

Strain on economy

The infected woman in Beijing had not travelled or had contact with infected people, authorities said, as they tested some 13,000 people living or working in the same area.

Health official Pang Xinghuo told reporters the virus had been found on the surface of a letter the infected person had received from Canada, as well as inside the unopened letter.

Dozens of letters from the same batch were tested, and five showed positive traces of COVID-19, she said, including samples from inside unopened letters.

The strain was different from Omicron cases in China, and similar to strains identified from North America last month, she added.

“We come to the conclusion that the possibility of virus infection through inbound objects cannot be ruled out,” she said.

Therefore, residents should “try to avoid buying goods from overseas during outbreaks”.

“If you receive overseas mail, you should wear masks and disposable gloves to reduce direct contact,” she said, advising people to “open the packages outdoors”.

Beijing’s theory that the virus did not originate in China but was imported in frozen food was judged “possible” but very unlikely in last year’s report from World Health Organization-appointed international experts.

China has linked a number of its virus clusters to products imported from overseas.

The Centers for Disease Control and Prevention in the US says on its website it is “possible” for people to be infected through contact with contaminated surfaces or objects — but the risk is low.

Within three days, there should be a 99 per cent reduction of virus traces left on surfaces.

Analysts have warned China’s ongoing zero-COVID approach — which includes targeted lockdowns and travel restrictions — will increasingly weigh on the economy.

Another 68 cases were reported across central Henan province, where partial lockdowns and mass testing have been rolled out for millions of residents.