The Korean military is facing mounting criticism after more than 80 percent of the 301-strong Cheonghae unit tested positive for the coronavirus while carrying out anti-piracy operations in the waters off Africa.

“The (COVID-19) test results on all 301 crew members of the unit showed that 247 tested positive and 50 negative. The samples of four individuals were undecipherable,” the Joint Chiefs of Staff said Monday.

The government sent two KC-330 tanker transport planes to bring home all of the service members on the navy’s 4,400-ton-class destroyer Munmu the Great. While 16 of them have been sent to local hospitals for treatment, most of the remaining personnel have been isolated on the ship.

The service members are expected to return to Korea on Tuesday afternoon. Once they arrive, the sailors will undergo another round of virus tests before being sent to medical facilities for treatment.

The worst mass infection in the military since the COVID-19 outbreak in the country last February first began with the unit first reporting six confirmed cases last Thursday. After that, the number of newly confirmed cases reached 61 on Sunday and 179 on Monday.

According to the Defense Ministry, all crew members had negative results from a PCR test before going onboard in February. But none of them had been vaccinated as it was before vaccinations for military personnel began.

“Our Cheonghae unit had the rights and reasons to call for vaccination from the UN,” Rep. Kang Dae-sik of the National Assembly’s National Defense Committee said Sunday.

“If (they) did not receive vaccines when they were embarking, active measures such as seeking cooperation from the UN should have taken place. At least, vaccinations should have been completed for the personnel who would make direct contact with locals at the port for loading supplies.”

Although more analysis and contact tracing are necessary before determining the route of infection, the destroyer’s record of operations shows a lack of caution amid the 21st century’s worst pandemic.

The destroyer docked at a harbor near the Gulf of Aden to load supplies from June 28 to July 1. A day after the ship left the port, one sailor reported symptoms of a cold. Instead of conducting COVID-19 tests, the unit just gave him cold medicine. The sailor was not put in isolation.

As several others started showing cold symptoms after a week, the unit conducted rapid diagnostic tests, which are not as accurate as the PCR tests, on 40 of the crew members on July 10. The results came out negative. Again, there were no additional disease control efforts during this period.

With cooperation from a nearby country, the unit sent samples of six sailors for the more accurate PCR tests on July 13. They came out positive after two days.

In short, the military had two weeks to implement stricter distancing guidelines or even isolation for the 301 service members since the first sailor showed symptoms of the coronavirus. If the unit decided to take the PCR tests and found confirmed cases earlier, the spread of infections could have been curbed.

Meanwhile, the military claimed that vaccine manufacturers banned the outbound shipment of vaccines. But health authorities said there have been no discussions on the matter.

“In regards to the assertion of the Korea Disease Control and Prevention Agency not allowing the outbound shipment of vaccines, the Joint Chiefs of Staff needs to check its facts. We have not talked about (the matter) in detail yet,” KCDC chief Jeong Eun-kyeong said in a regular press briefing Monday.

“However, since we would have to send the vaccines by plane, I believe that we figured it was difficult to carry them. So we could not supply the vaccines to (Cheonghae unit).”

Over 70 percent of some 1,300 troops on overseas missions have been fully vaccinated so far, including the crew members who will take over the mission of the Cheonghae unit, according to the Defense Ministry.

In the wake of the Navy sailors’ mass infection, the ministry and the JCS plan to come up with crisis management guidelines for infectious diseases for overseas units.