Novel coronavirus subvariant XBB.1.5 is 'most transmissible', says WHO

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World Health Organization officials have expressed concern Wednesday about a new omicron subvariant of the coronavirus – his most communicable yet – while urging China to be more open with its data on infections and deaths amid a recent surge there.

Declining global coronavirus surveillance, incomplete data from China and an increase in covid-19 deaths worldwide are concerning, said Maria Van Kerkhove, WHO’s technical lead on covid-19, during of a press conference. “It’s not just about knowing which variants are circulating. We need the global community to assess them, examine mutation by mutation to determine if these are new variants circulating.

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Mike Ryan, executive director of the WHO’s health emergencies program, who spoke at the same press conference, said he had met with Chinese health officials last week and reiterated his concerns regarding China’s data, including its definition of a covid-19 death, which he said he considered too narrow.

The Associated Press reported last month, only covid-19 deaths from pneumonia or respiratory failure were counted in China’s official counts. Chinese authorities have also stopped tracking asymptomatic cases, according to the precedent Washington Post report.

The newly tightened criteria for what China considers a covid-related death have frustrated overseas health officials trying to prepare for potential mutations of major epidemics. It has also heightened suspicion that the official death toll and number of infections in the world’s most populous country represent a significant undercount.

China recorded at least 120,000 new weekly cases or more in December, According to WHO. The number of weekly deaths varied between 240 and 440 during this period, according to these figures, despite reports overwhelmed hospital wards, funeral homes and crematoriums.

“We believe the current number published in China underrepresents the true impact of the disease in terms of hospital admissions, in terms of ICU admissions and particularly in terms of deaths,” Ryan said.

Tedros Adhanom Ghebreyesus, director-general of the WHO, also urged Chinese authorities on Wednesday to provide “faster, regular and reliable data on hospitalizations” and “more complete real-time viral sequencing”.

Chinese officials have said the dominant version of the coronavirus in China is the omicron BA.5 subvariant, Van Kerkhove told reporters, although she said more sequencing needed to be done there.

BA.5 shares common mutations with the BA.2 omicron subvariant, but each has unique traits, according to research done in the UK and Austria and published in the journal Nature last month.

XBB is a recombinant of the BA.2.10.1 and BA.2.75 sublines, According to WHO. He has quickly become dominant in the northeastern United States.

Michael Baker, professor of public health at New Zealand’s University of Otago in Wellington, said it will take “several weeks” to see if XBB.1.5 causes more severe illness than earlier versions of the coronavirus, as the hospitalizations and deaths occur after an increase in infections and it takes time to measure how many of these illnesses can be attributed to XBB.1.5.

He added that an XBB.1.5 wave appears “likely”.

But even if XBB.1.5 turns out to cause less severe disease, being more infectious is still a concern, Baker said.

“As we’ve seen with the omicron variant in general, its high infectivity means that in many countries it has caused more illness and death than any previous variant,” he said.