How serious are new Covid-19 variants and where do they come from?

Ever since China ended its “zero-Covid” policy late last month, its hospitals have been overwhelmed by cases. But as concerns grow about the threat of new variants, Beijing has been criticised by global health bodies for a lack of transparency about the prevalence of the virus in the country.

At least 15 countries have introduced mandatory Covid testing for travellers arriving from China, mostly to ensure that no dangerous variants go undetected. The UK Health Security Agency, for example, has asked hospitals to sequence all viral samples from patients who have arrived from China that are hospitalised with Covid.

But are surging infection rates likely to lead to powerful variants from China or other countries with current high caseloads, such as the US? The chances are seen as low by many epidemiologists though they remain concerned that a lack of transparency in some countries could hinder detection.

What do we know about variants in China?

Gisaid, the global repository of genomes that allows scientists to track coronavirus as it mutates, on Tuesday said the samples uploaded to its database “all closely resemble known globally circulating variants seen in different parts of the world between July and December”.

Data presented to the World Health Organisation (WHO), an analysis of which was published on Wednesday, reached a similar conclusion. “No new variant or mutation of known significance is noted in the publicly available sequence data,” the health body said.

Peter Bogner, Gisaid’s chief executive, said it was “a grave mistake” to focus solely on acquiring timely data from China, because “new variants of significance can appear anywhere in the world”.

“Unfortunately we’re starting to see surveillance gaps appear across the globe,” he told the Financial Times.

“[But] China is actively ramping up its efforts in making available more data on circulating variants, so our surveillance lens in Asia is getting sharper by the day. It would thus be advisable to trust science over politics.”

Why do passengers from China face restrictions?

Western health officials say privately that the checks on travellers have mostly been introduced to avert potential variants spreading undetected but that the current measures are not justified by any existing threat. One senior European official, who declined to be named, said it was a “political” decision, citing “governments that want to be seen as protecting their own people”.

China was criticised earlier in the pandemic for its reticence on publishing Covid data, which may have made western officials wary of Beijing’s approach, according to officials familiar with the thinking in European capitals. Beijing’s strict zero-Covid policy for most of the past three years in turn makes restrictions on arrivals from China more politically palatable, they said.

Entry restrictions for passengers from China

Australia, from January 5th

Travellers boarding flights from China, Hong Kong or Macau will need to show a negative Covid test result taken within 48 hours of travel to Australia.

Canada, from January 5th

All passengers from China, Hong Kong or Macau need to show a negative result from a test taken within two days of departure. Measure in place for initial 30 days.

France, from January 5th

Arrivals from China to present a negative Covid test result taken no less than 48 hours before departure. Passengers will also be required to wear a mask in flight and agree to random testing on arrival.

India, from January 1st

Requirement of a negative Covid test for those travelling from China (as well as Japan, Hong Kong, Thailand, Singapore and South Korea).

Israel, from January 5th

No entry for non-Israeli travellers from China without a negative PCR test.

Italy, from December 28th

All airline passengers face a mandatory Covid test on arrival and quarantine if the test is positive.

Japan, from December 30th

Initially, passengers from China (or who have travelled there in the past seven days) tested for Covid upon arrival. From January 8th, a negative test result taken within 72 hours of departure will also be required.

Malaysia, from December 30th

Temperature screening of all passengers from China for fever.

Morocco, from January 3rd

Access to the north African country is prohibited for all travellers, regardless of their nationality, arriving from China.

Qatar, from January 3rd

Travellers from China will need to provide a negative Covid test result within 48 hours of departure.

South Korea, from January 5th

Passengers arriving from China require a negative PCR test 48 hours before entry, or rapid antigen test within 24 hours followed by a PCR on arrival. Restrictions for short-term visas for Chinese nationals.

Spain, from December 31st

Passengers from China must show a negative test result within 24 or 72 hours of departure for Spain, depending on the type used, or be fully vaccinated.

Taiwan, from January 1st

Covid testing on arrival for those arriving from the Chinese mainland by air or sea. Those testing positive can isolate at home.

UK, from January 5th

Arrivals to the UK from China will be required to show a negative Covid test taken no more than two days before departure. A sample of passengers will also be tested on arrival.

US, from January 5th

Passengers arriving from China, Hong Kong, and Macau must present a negative Covid test taken no more than two days before departure.

Selected countries shown source: FT research

The current “intense” rates of transmission made it “understandable” that countries were taking steps to protect their citizens, the WHO said on Wednesday. Moreover, the 13 million cases reported to WHO in the past month were considered to be an “underestimate”, said the Geneva-based health body.

Mike Ryan, head of WHO’s emergencies programme, said some countries had opted for caution as a hedge against new variants amid a relative lack of data, adding it “would be much better if we had much more extensive sequencing”.

Where do new variants come from?

Viruses inevitably undergo genetic mutations as they reproduce within their hosts. A few variants prosper because they spread more readily between people than existing strains, by overcoming their immune defences and binding themselves more efficiently to human cells.

There are competing theories about exactly where new variants originate, because it is impossible to identify the true patient zero, the first carrier of the virus.

The most popular view among virologists is that most significant variants result from chronic infection in an immunosuppressed person who cannot clear the virus for several months, giving a series of mutations time to develop.

Which variants thrive will depend on a population’s immunity levels as determined by rates of previous infection or vaccination. Strains of Omicron, the dominant variant in many countries since late 2021, which are now surging through China, may not be best adapted to transmit through European or US populations with different immune profiles.

Which variants are spreading beyond China?

Omicron’s descendants dominate transmission worldwide. The original Sars-CoV-2 virus and Omicron’s predecessor variants, officially denoted by Greek letters, are almost extinct. The Omega subvariant causing most concern among virologists is XBB.1.5, which seems to have originated in the north-eastern US in October and is spreading rapidly across the country.

According to the US Centers for Disease Control and Prevention, XBB.1.5 was responsible for 40 per cent of US cases during the last week of December. The variant is also on the increase in Europe and has been identified in more than 25 countries, the WHO said on Wednesday.

XBB.1.5 is informally called Kraken after the mythological sea monster, one of a number nicknames that scientists have applied “to help people keep track of the ever-growing variant soup”, said Ryan Gregory, an evolutionary biologist at Canada’s University of Guelph. “There are now more than 650 Omicron subvariants.”

Kraken is descended from XBB or Gryphon – itself a hybrid of two Omicron BA.2 descendants. A key mutation enables XBB.1.5 to transmit rapidly between people by evading antibodies conferred by previous infection or vaccination, while at the same time binding more tightly to human cells.

“While there’s still much to learn about this variant, it doesn’t have the look of a ‘scariant’,” said Eric Topol, professor of molecular medicine at Scripps Research in California, referring to the term he coined for strains that sound scary but are not really dangerous. “This one is the real deal and we’re betting on our immunity wall of infections, vaccinations, boosters and their combinations to help withstand its impact,” he said. – Copyright The Financial Times Limited 2023