A new highly mutated coronavirus variant has been detected in Switzerland and South Africa, prompting scientists to raise alarm bells over a possible explosion of Covid-19 cases.
The Omicron offshoot, called BA.2.86, carries more than 35 mutations in key portions of the virus compared with XBB.1.5 – the dominant variant through most of 2023.
The World Health Organisation (WHO) last week said it was "monitoring" the new strain after a small number of cases related to the strain were found in Israel, Denmark, Britain and the US.
The strain was first spotted in Denmark on 24 July after the virus from a patient at risk of becoming severely ill was sequenced. It has since been detected in other symptomatic patients, in routine airport screening, and in wastewater samples in a handful of countries.
In England, Covid-19 cases have almost doubled in a month and one case related to BA.2.86 was detected in London, authorities announced on Friday.
There have been nine such cases detected as of 23 August and the variant was also found in wastewater in Switzerland, Reuters reported.
"It is still low numbers," said Maria Van Kerkhove, an epidemiologist and lead for the Covid response at the WHO. That the known cases are not linked suggests it is already circulating more widely, particularly given reduced surveillance worldwide, she said.
"Governments cannot drop the ball," Ms Van Kerkhove said, adding that the coronavirus continues to circulate, evolve, infect and kill people.
While concerns remain over the mutation, a dozen scientists around the world said it was unlikely to cause a devastating wave of severe disease and death given immune defences built up following large-scale vaccinations.
Scientists are testing how well updated Covid-19 vaccines will work against BA.2.86.
Ms Van Kerkhove noted that vaccines have been better at preventing severe illness and death than re-infection.
"We are in a very different phase (of the pandemic) than if this popped up in the first year," said Marion Koopmans, a Dutch virologist who advises the WHO.
The US Centers for Disease Control and Prevention (CDC) and others spotted the new variant last week and held meetings with scientists throughout the weekend, Nirav Shah, principal deputy director of the health body said.
The discovery came as new Covid hospitalisations leaped by 21.6 per cent this week, with an estimated 2,000 Americans requiring specialist care per day, according to figures released by the CDC.
It appears that current tests and medications remain effective against BA.2.86, although the variant may be more capable of causing infection in vaccinated people and those who have had Covid-19, according to a risk assessment report by the CDC.
There is no indication that the new variant causes severe illness, it added.
"When we do sequencing now, it's like (finding) a needle in a haystack," said Tyra Grove Krause, a Danish epidemiologist at the Statens Serum Insitute which identified three BA.2.86 cases.
The WHO said Covid-19 testing has declined by 90 per cent worldwide from the peak. Testing has also plummeted in the US, and sequencing is down by around 90 per cent, said Ashish Jha, who served as White House COVID-19 Response Coordinator until June 2023.
Data from hospital admissions, emergency room visits, deaths, wastewater sampling and sequencing, including at airports, has helped fill in the global picture, he said.
Pfizer and Moderna are expected to roll out updated vaccines that will be effective against recent strains in October.
