The World Health Organisation and US health authorities said on Friday they are closely monitoring a new variant of Covid-19, although the potential effect of BA.2.86 is currently unknown.
The WHO classified the new variant as one under surveillance "due to the large number (more than 30) of spike gene mutations it carries", it wrote in a bulletin about the pandemic late on Thursday.
So far, the variant has been detected only in Israel, Denmark and the US.
There are only four known sequences of the variant, according to the WHO.
"The potential impact of the BA.2.86 mutations are presently unknown and undergoing careful assessment," the WHO said.
The organisation is currently monitoring upwards of 10 variants and their descent lineages.
The US Centres for Disease Control (CDC) confirmed it is also closely monitoring the variant, in a message on the social platform X, formerly known as Twitter.
Most countries that established surveillance systems for the virus have since dismantled operations, determining it is no longer as severe and therefore could not justify the expense – a move the WHO has denounced, calling instead for stronger monitoring.
In the last reporting period between July 17 and August 13, more than 1.4 million new cases of Covid-19 were detected and more than 2,300 deaths reported, according to a WHO statement.
The case load represents a rise of 63 per cent from the previous 28-day period while deaths were down by 56 per cent.
As of August 13, there were more than 769 million cases of Covid-19 confirmed and more than 6.9 million deaths worldwide, although the real toll is expected to be much higher because many cases went undetected, particularly in developing countries with weak health infrastructure.
The new lineage, which has 36 mutations from the currently-dominant XBB.1.5 Covid variant "harks back to an earlier branch" of the virus, said Dr S Wesley Long, medical director of diagnostic microbiology at Houston Methodist.
He said it remains to be seen whether BA.2.86 will be able to out-compete other strains of the virus or have any advantage in escaping immune responses from previous infection or vaccination.
Early analysis indicates that the new variant "will have equal or greater escape than XBB.1.5 from antibodies elicited by pre-Omicron and first-generation Omicron variants," said Jesse Bloom, a virologist at the Fred Hutchinson Cancer Centre.
The Omicron subvariant XBB.1.5 is the strain targeted by vaccines in upcoming Covid booster shots.
Dr Bloom's slides note that the most likely scenario is that BA.2.86 is less transmissible than current dominant variants, so never spreads widely, but more sequencing data is needed.
"My biggest concern would be that it could cause a bigger spike in cases than what we have seen in recent waves," Dr Long said. "The boosters will still help you fight off Covid in general."
- With reporting from agencies
