Taipei, May 6 (CNA) Pilots and flight attendants with Taiwan's flagship carrier, China Airlines (CAL), are now required to quarantine for five days instead of three on arrival, and they will be tested more often for COVID-19, health authorities said Thursday.

The Central Epidemic Command Center (CECC) said it was revising its protocols for CAL flight crews amid an outbreak of COVID-19 among them, which has now reached 12 cases.

Effective immediately, CAL pilots and flight attendants returning to Taiwan on long-haul flights will have to remain in quarantine for five days, after which they will have to follow "enhanced self-health management" rules for nine days, the CECC said.

During the nine-day period, they will not be permitted to take public transportation or visit crowded areas, and they will be required to keep a record of their daily activities and everyone with whom they come into contact, according to the CECC protocols.

In addition, CAL flight crew members will be tested for COVID-19 five times during the quarantine and enhanced self-health management period, between the fifth and 14th day after their arrival, the CECC said.

CAL crew members who work on one-day return flights that do not require overnighting in another country will be asked to follow self-health management protocols for 14 days after they return to Taiwan, the CECC said.

The protocols during the 14-day period of self-health management include wearing a mask at all times outside their homes, checking their temperatures twice per day, and avoiding large gatherings and dining out, according to the CECC.

They will be tested for COVID-19 on the seventh and 14th day after their return to Taiwan, the CECC said.

For flight crews with other Taiwan airlines, the protocols remain unchanged, which means those on long-haul flights are required to quarantine for three days upon return, after which they will be tested once for COVID-19 and will be asked to conduct self-health management for 11 days, once they test negative, according to the CECC.

Crew members on short-haul flights operated by those airlines only have to follow self-health management protocols for 14 days after their return to Taiwan, the CECC said.

The new protocols for CAL were introduced amid an outbreak in which 11 of the airline's pilots and one of its flight attendants have tested positive for COVID-19 over the past two weeks. Eight relatives of CAL pilots have also contracted the disease, according to the CECC.

The CECC said it was not sure how the pilots and flight attendant had contracted the virus, but it had determined that some of the CAL cases were linked to the infections at an airport hotel in Taoyuan, where six employees have tested positive to date.

At a press conference Thursday, Minister of Health and Welfare Chen Shih-chung said that with the introduction of the new protocols, the CECC hopes to strike a balance between preventing wider spread of the disease and allowing the continuation of CAL's operations.

The measures were not imposed on other Taiwan airlines because they do not have cluster infections, said Chen, who heads the CECC.