The micron sub-variant XBB.1.5 is the most transmissible variant of covid so far, WHO says

The micron XBB.1.5 sub-variant currently prevalent in the US is the most infectious variant of covid-19 so far, but it does not appear to make people sicker, according to the World Health Organization.

Maria van Kerkhove, the World Health Organization’s technical lead for Covid-19, said global health officials are concerned about how quickly the subtype is spreading in the northeastern U.S. The number of people infected with XBB.1.5 in the U.S. is doubling roughly every two weeks. making it the most common variant currently circulating in the country.

“This is the most transferable sub-variant that has been discovered so far,” Van Kerkhove told reporters at a news conference in Geneva on Wednesday. “The reason for this is the mutations that are within this omicron subversion that allow this virus to stick to the cell and reproduce easily.”

So far, it has been detected in 29 countries, but it could be even more widespread, Van Kerkhove said. Tracking variants of Covid has become difficult as genomic sequencing declines worldwide, she said.

The WHO does not yet have any data on the severity of the XBB.1.5 virus, but there is currently no indication that people are getting sicker than previous omicron versions, Van Kerkhove said. A WHO advisory group that monitors Covid variants is conducting a risk assessment of XBB.1.5, which it will publish in the coming days, she said.

“The more this virus circulates, the more opportunities it will have to change,” Van Kerkhove said. “We expect further waves of infections around the world, but this does not necessarily translate into further waves of deaths because our countermeasures continue to work.”

The scientists say XBB.1.5 is about as good at evading antibodies from vaccines and infection as its relatives XBB and XBB.1, which have been the two most immune-evading sub-variants to date. But XBB.1.5 has a mutation that binds more tightly to cellswhich gives it a growth advantage.

While XBB.1.5 is spreading rapidly in the US, China is grappling with a surge in cases and hospitalizations after abandoning its Covid-free policy in response to social unrest late last year. U.S. and global health officials have said Beijing is not sharing enough data about the surge with the international community.

“We continue to ask China for faster regular reliable data on hospitalizations and deaths and for more comprehensive real-time sequencing of the virus,” WHO Director-General Tedros Adhanom Ghebreyesus told reporters in Geneva on Wednesday.

A growing number of countries, including the US, are requiring air travelers from China to test negative for Covid before boarding planes. China’s foreign ministry said such measures had no scientific basis and accused governments of manipulating Covid for political purposes. But the WHO director said the requests were understandable given the limited data coming out of China.

“Because circulation in China is so high and comprehensive data is not available, it is understandable that some countries are taking measures that they believe will protect their citizens,” Tedros said on Wednesday.

China’s Centers for Disease Control and Prevention shared data with the WHO on Tuesday showing that the BA.5, BA.5.2 and BF.7 sublines account for about 98% of all infections in the country. But Van Kerkhove said China is not sharing enough sequence data from the big country.

“It’s not just about knowing which versions are circulating,” Van Kerkhove said. “We need the global community to evaluate them, to look mutation by mutation, to see if there are any of these new variants that are circulating in China, as well as around the world.”