A massive surge in Omicron infections in China likely means new subvariants—and potentially worse.

China has over 1.4 billion people and is currently in the midst of the largest deadly outbreak of COVID-19. Daily COVID-19 cases equate to more than the population of Australia; hospitals are overwhelmed, as are crematoria, and over a million people are expected to perish within weeks.

The elderly are most at risk with only half of those over 80 being fully vaccinated. Moreover, Chinese vaccines have only moderate effectiveness compared to those used in Western Countries, and antivirals are in short supply.

January 7^th marked the beginning of Chun Yun, the 40-day period of travel for Chinese New Year. It is the largest annual mass migration of people on Earth. In a short period of time, over 2 billion passenger trips are undertaken, with many travelling from urban to rural areas.

Widespread Covid-19 infection in so many Chinese people will likely result in co-infections with Omicron subvariants, and possibly other Coronaviruses, potentially leading to recombination, resulting in a new virus variant.

A new variant is likely to be more transmissible, which has been observed as the virus evolves, with potentially greater severity, which however, has not been observed to date. A further concern is that vaccine-induced immunity against severe disease may be evaded, but so far that has not eventuated anywhere in the world. For example, the Omicron subvariant XBB.1.5 is currently surging in the USA and elsewhere but vaccines are still effective.

Might the situation in China allow Omicron to move on to Pi and eventually become Omega?

Some immunologists point to the lack of immunity to Covid-19 in China (because of zero-Covid restrictions, much fewer infections, low vaccination rates, and the use of vaccines that give only moderate protection), and suggest that this level of immunity is unlikely to drive the emergence of a new variant. However, hundreds of millions of Omicron infections with a virus that routinely mutates, must at least produce new subvariants of Omicron.

The zero-covid policy in China lasted for over a thousand days until early December, far more than a Victorian lockdown, achieving success through mass testing and draconian quarantine. However, the Chinese government abruptly dismantled control measures in response to protests and a flagging economy—and widespread outbreaks have occurred, seeded from surrounding nations.

WHO notes that official statistics from China dramatically under-report hospitalisations and deaths. We need much better surveillance, including timely and accurate reporting of cases and deaths, and genetic sequencing of viruses in order to detect new mutations in a timely way, otherwise it’s possible that thousands of cases of a new variant may arise before it is even recognised. Rapid detection and reporting are critical in our fight against COVID-19.

It is incumbent on all countries to continue genomic surveillance in a timely and accurate way. Over 14 million COVID-19 genomes from all parts of the globe have been sequenced and shared within the scientific community via the international GISAID database.

These data have guided public health decisions, allowed the development of rapid tests and the production and updating of vaccines, and informed research into drug development. In addition, the mutations identified give some insight into whether new mutations will worsen transmissibility and severity.

Chinese laboratories continue to increase their efforts in genomic surveillance and share their latest genome sequence data from recent cases in 14 provinces. Currently the data shows that while new Omicron sub-variants are arising, there is no sign of a new variant yet, and that while these viruses remain highly transmissible, severity is not significantly different to date.

Rapid detection will give us the most protection and the earliest signal to act quickly if we need to.

Robert Booy is a consultant paediatrician, infectious disease expert and clinical professor at University of Sydney.

Gary Grohmann is a consulting virologist and adjunct professor at the University of Sydney.