TOKYO (BLOOMBERG) - Japan will allow medical workers who have been identified as close contacts of Omicron cases to keep working, after staff absences caused by a 14-day quarantine period stressed the health system in an area suffering from a large outbreak.

The health-care staff can continue working as long as they pass daily tests, the country's health minister Shigeyuki Goto told reporters on Wednesday.

The government is moving to allocate resources to those who need them the most as cases surge in Japan, which had all but snuffed out its wave of the Delta variant.

Nationwide new Covid-19 cases jumped by 13,044 on Wednesday (Jan 12), the highest daily figure since September.

In the southern island of Okinawa, the site of one of the nation's biggest Covid-19 outbreaks, the number of health care workers taking sick leave climbed to a record, forcing some medical institutions to limit their capacity to accept emergency patients, according to local reports.

A health ministry panel plans to advise the government to cut the length of quarantine required for all other close contacts of Omicron cases to 10 days from the current 14 days after acknowledging the new variant's short incubation period, the Yomiuri newspaper reported Thursday without citing anyone.

Prime Minister Fumio Kishida said on Thursday it's under consideration.

"Experts have pointed out that it's important to take appropriate measures so that society, including the health-care system, can function properly," Kishida told reporters in Tokyo.

If Japan decides to cut the quarantine period for all people who have been identified as close contacts of Omicron, it will follow countries like the US and Australia, which require an isolation period of at least 5 days and 7 days respectively.

Tokyo's government raised its Covid-19 alert to the second-highest level on a four-tier system, amid warnings that Omicron is quickly replacing the Delta variant and can cause social disruption.

A panel of experts advising the prefectural administration said new daily cases can exceed 10,000 and there is a need to prepare a system that allows patients to be swiftly moved into isolation to stem the new wave of infections.

The panel also raised the health system alert to the third highest of all four stages saying it's time to prepare a system that allows the government to swiftly move patients to isolation in order to respond a new wave of infections.

Japan is rolling out booster vaccinations to health-care workers and the elderly. The government plans to offer boosters to the rest of the population starting around March. Almost 80 per cent of Japanese residents are fully vaccinated with two shots, making it one of the most immunised nations among developed countries.

The government has also increased the number of medical institutions that can conduct visits to treat people at home in isolation by 30 per cent to 16,000 from November, Goto said.