Healthcare workers in the United States who test positive for Covid-19 but are asymptomatic can return to work after seven days in isolation, provided they test negative, the Centres for Disease Control and Prevention said.

The new guidance cuts the quarantine time from a previously recommended 10 days, which the CDC said was in preparation for an anticipated increase in Omicron cases. Omicron now accounts for 73 per cent of coronavirus infections in the United States, the CDC said, according to a Reuters report.

The CDC said the quarantine time can be cut further if there are staffing shortages due to Covid-19, adding that healthcare workers who have been fully vaccinated, including a booster, do not need to quarantine at home following high-risk exposures.