Did Omicron arrive in China’s capital Beijing by mail from Canada?
- City’s first case of the Covid-19 variant received a letter from Toronto with traces of the virus, health authorities say
- Canada’s public health agency and other experts around the world say there is low risk of spreading through goods or packages
“We do not rule out the possibility that the person was infected through contacting an object from overseas,” she said.
This view is shared by Canada’s public health agency, which has previously said there is no evidence of Covid-19 being transmitted by imported goods or packages.
In a Q&A section on its website, the Canadian post office cites assurances from the country’s public health agency and the World Health Organization that the risk when handling mail, including international deliveries, is low.
“Because of the poor survivability of coronaviruses on surfaces, there is a low risk of spread from products or packaging shipped over a period of days or weeks,” it said.
On Monday, Pang said health authorities investigated the man’s post as a potential source of infection when they learned that he occasionally received overseas mail.
Testing found the Omicron variant present on the letter, which had travelled via the US and Hong Kong before arriving on January 11, she said.
Liao Lingzhu, deputy director of the Beijing postal administration, said the express letter had arrived at the capital airport from Toronto on January 10.
All employees who handled the mail – which was sanitised by an express courier before delivery the next day to the city’s Zhongguancun area – are in quarantine. Eight people who may have been in contact with the letter have tested negative.
However, authorities said they found traces of the virus on a further five pieces of mail among 54 that were sent from the same place to a different address in China. One positive sample was taken from the outside of a package, and four pieces of contaminated paper were found inside mail that had not been opened before they were checked.
Genome sequencing of samples from the patient showed that the Omicron strain was similar to the one that was spreading in Singapore and North America in December, but differed from the one now circulating in other parts of China.
Pang said the infected person had not travelled outside Beijing in the 14 days before developing a sore throat on January 13, followed by fever a day later. Repeated swab tests from January 14 confirmed the presence of Omicron and that the patient was in the early stage of the disease.
The disease control centre said it could find no evidence that the patient had been in contact with high-risk groups, such as arrivals from overseas or affected parts of the country, or other positive cases or their close contacts.
All 69 close contacts of the Beijing case had tested negative, along with 16,000 swab test samples collected from other potential contacts and 811 samples collected from the environment. The authorities also ruled out the possibility that the patient could have contracted the virus via cold-chain transmission.
The centre said that residents should minimise their purchases of goods from overseas and wear masks and gloves when opening mail from high-risk countries. It recommended that letters and packages should be opened outside the home and sanitised.
Its health officials have also suggested repeatedly that the cold chain may have brought the coronavirus to Wuhan in late 2019 in the first place, and have urged studies to be carried out internationally.
However, the theory has been dismissed by most scientists in other countries as highly unlikely. Although samples taken from the surface of an object can test positive, they may not be infectious, because they may be dead traces of the coronavirus. Even if a sample can infect living cells in a laboratory, it takes a certain viral load to infect a person.
So far most of the research – largely preprint studies – has come from Chinese scientists.
Also on Monday, authorities in the southern city of Shenzhen said that the first local Omicron infection there, which was identified on Sunday, could have arrived via the cold chain.
They said that this strain, too, differed from that circulating elsewhere in China, and that the infected person had handled a courier delivery from North America last Wednesday before testing positive on Saturday.