Coronavirus: new variants raise questions about sustainability of China’s zero-Covid policy

Two sublineages of Omicron – BA.4 and BA.5 – have quickly become the dominant strains in many countries, including the United States, Britain and Australia.

Scientists say the two subvariants, which are close relatives, are offshoots of the highly transmissible Omicron BA.2, with additional mutations in the spike protein that make them the most infectious Covid-19 lineages so far.

However, their status as the most infectious Covid-19 variants may only hold true for a while, as they now face the challenge of yet another Omicron spin-off, called the BA2.75 and nicknamed “Centaurus” by the science community.

The World Health Organization is closely monitoring the new subvariant, which first emerged in India in late June, but said it was still too early to tell if it could outcompete BA.4 or BA.5 or if it caused more severe sickness.

The speedy emergence of sublineages one after the other is not a surprise, as RNA (ribonucleic acid) viruses like Sars-CoV-2 – the coronavirus that causes Covid-19 – evolve quickly. But that also means China, which continues to hold on to a zero-Covid policy, will constantly have to catch up with ever-increasingly transmissible variants, with the race becoming ever more difficult.

On Friday, Chinese officials said the task of preventing local transmissions of BA.4 and BA.5 caused by imported cases and contaminated goods was “complex and grave”.

They vowed to step up measures such as putting people working in customs and at ports in closed loops, disinfecting imported goods, and quarantining people arriving from overseas, even though such travellers now only need to spend seven days in quarantine in government facilities, down from 14, with an additional three days at home.