Washington, Dec 15 (IANS): Masks in indoor and public settings are back in some parts of the US as Covid-19 cases are soaring, while a recent study by researchers in Hong Kong shows that the explosive growth of infection rates in China could also lead to mutations of the virus.

The Centers for Disease Control and Prevention (CDC), however, is yet to issue any fresh guidelines on masks but Poynter.org quoted CDC Director Dr Rochelle Walensky as saying that it is something that they are actively looking into at the CDC.

"In the meantime, what I do want to say is, one need not wait for CDC action in order to put a mask on," said Walensky.

Santa Clara County on Thursday moved up to what the CDC deems a high Covid-19 community level, based on case and hospitalisation data, so did Los Angeles County.

According to the government weekly update, 13.7 per cent of Americans live in communities now rated at "high" Covid-19 community levels, up from 4.9 per cent of the population last week.

New York Health Commissioner Dr. Mary Bassett and Education Commissioner Betty Rosa have issued a letter, saying schools should consider encouraging students and teachers to wear masks once again.

"The number of laboratory-confirmed flu cases has nearly tripled over the past three weeks and flu hospitalisations have more than doubled. In addition, Covid-19 continues to pose a significant threat, particularly for unvaccinated or under-vaccinated New Yorkers, as the virus remains one of the leading causes of death in the United States," read the letter.

"In response, we are urging a community-wide approach, inclusive of schools, to again take precautions this holiday season and winter that can prevent the spread of respiratory viruses and protect young children, older individuals, and those with underlying health conditions," they added.

A CDC study also found that between January 2020 and June 2022, long Covid was implicated in at least 3,544 deaths in the US alone.

Meanwhile, Beijing has been hit with a significant, and spreading, outbreak - a first for the Chinese capital since the beginning of the pandemic, reports CNN.

"China's National Health Commission (NHC) gave up trying to keep track of all the new Covid cases, announcing it would no longer include asymptomatic infections in its daily count," said the report.

It had previously reported these cases, albeit in a separate category from "confirmed," or symptomatic ones.