NEW YORK (NYTIMES) - As global concern rose on Friday (Nov 26) about a new coronavirus variant, Governor Kathy Hochul declared a state of emergency in New York, giving her the power to order hospitals to limit non-essential procedures to boost capacity in facilities.

The new variant, called Omicron, has officially been named a "variant of concern" by the World Health Organisation.

The designation means that the variant has mutations that might make it more contagious or more virulent, or make vaccines and other preventive measures less effective - although none of those effects has been established.

The new measures in New York, where Covid-19 caused thousands of deaths last year, will take effect next Friday. They are a far cry from the strict, societywide restrictions that accompanied the early stages of the pandemic.

Still, the quick action by Ms Hochul suggests the high level of concern not just about rising numbers of new cases across the state in recent weeks but about the Omicron variant, which has prompted several countries, including the United States, to restrict travellers from southern Africa.

"We continue to see warning signs of spikes this upcoming winter, and while the new Omicron variant has yet to be detected in New York state, it's coming," Ms Hochul, a Democrat, said in a statement, adding that vaccination remains a critical tool in fighting the virus.

Rates of positive tests in New York have crept up recently, even as vaccination rates have improved, with some counties recording positivity rates of more than 10 per cent.

In the two weeks before Thanksgiving Day, the daily average of new cases reported in New York rose 37 per cent, to 6,666, according to a New York Times database. More than 56,000 people have died of the disease in New York.