Two new Omicron subvariants spreading quickly in New York

NEW YORK • Two new versions of Omicron, the coronavirus variant that has swept through the world in the past few months, are circulating in New York state and may be responsible for rising infections in the region over the past few weeks, state health officials said.

The appearance of these variants, both of which evolved from subvariant BA.2, may explain why New York has been the United State's national hot spot in the past few weeks, officials said on Wednesday. So far, the new versions do not appear to cause more severe disease than previous variants, the officials said.

The two new versions have a growth advantage of about 25 per cent over BA.2, which until now was the most contagious version of the coronavirus.

But it is unclear whether they spread more quickly because of greater contagiousness or an improved ability to sidestep the body's immune defences.

One of the new subvariants has a mutation that has been shown to help dodge immunity.

"It's just a reminder that we're not out of the woods with regard to this virus, and people should continue to take precautions and get fully vaccinated if they haven't completed their course," said Dr Kirsten St George, a virus expert for the state who led the work.

Last month, the subvariants called BA.2.12 and BA.2.12.1 accounted for more than 70 per cent of new cases in central New York state, a figure that has risen above 90 per cent. The subvariants comprise one in five cases in the Finger Lakes region.

The subvariants have also been detected in more than 40 other countries and in more than 30 states across the US, said Dr St George.

Both new forms of the virus evolved from BA.2, which accounts for nearly 81 per cent of coronavirus infections in New York. A previous version of Omicron - BA.1 - sent infections soaring over the winter to unprecedented highs.

New York State Department of Health officials have been tracking the spread of variants since late 2020 and significantly stepped up those efforts last year. But with the rise of rapid testing at home, the state may be sequencing fewer than 5 per cent of new infections, Dr St George said.

US health officials on Wednesday extended by 15 days a US mandate requiring travellers to wear masks on aeroplanes, trains and in transit hubs.

The extension would keep the requirements, which had been set to expire on April 18, in place until May 3 amid an increase in Covid-19 cases.

As Covid-19 case numbers rise in some parts of the US, mask mandates have crept back. Philadelphia said it will reinstate its mask rule starting next Monday, requiring masks in indoor public settings such as restaurants, schools and businesses.

NYTIMES, REUTERS