The World Health Organisation says that the recently discovered subvariant of the highly contagious Omicron coronavirus strain has now been detected in 57 countries, while in some countries, the sub-variant now accounts for more than half of all sequenced Omicron cases. It said little was known yet about the differences between the sub-variants but several studies have suggested that BA.2, also known as the “stealth variant”, was more infectious than the original sub-lineage. Al Jazeera reports though that Maria Van Kerkhove, an epidemiologist and the WHO’s technical lead on the coronavirus pandemic, said there was “no indication that there is a change in severity” in the BA.2 sub-variant.