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New coronavirus subvariant XBB.1.5 'more transmissible', says WHO

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

The decline in global surveillance of the coronavirus, incomplete data from China and an increase in deaths from covid-19 around the world are concerning, Maria Van Kerkhove, WHO technical lead on covid-19, said at a press conference. “It’s not just a matter of knowing which variants are circulating. We need the global community to evaluate them, look mutation by mutation to determine if any of these are new variants that are circulating.”

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Mike Ryan, executive director of the WHO’s health emergencies program, who was speaking at the same news conference, said he had met with Chinese health officials last week and reiterated concerns about China’s data, including its definition of death from Covid-19. 19, which he said he saw as too narrow.

The Associated Press reported last month that 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 an earlier report by The Washington Post.

The newly tightened criteria for what China considers a Covid-related death frustrated health authorities abroad trying to prepare for potential mutations of large outbreaks. Suspicion has also grown that the official death toll and number of infections in the world’s most populous country represent a significant undercount.

China had at least 120,000 new cases weekly or more in December, according to the WHO. The number of weekly deaths varied between 240 and 440 during that period, according to these numbers, despite reports of overcrowded hospital wards, funeral homes, and crematoria.

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

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

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

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

XBB is a recombinant of BA.2.10.1 and BA.2.75 sublines according to WHO. It quickly became dominant in the northeastern United States.

Michael Baker, professor of public health at the University of Otago in Wellington, New Zealand, said it will take “many weeks” to see whether XBB.1.5 causes more severe illness than previous versions of the coronavirus because 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 looks “likely”.

But even if XBB.1.5 does 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.