South Korea’s anti-piracy Cheonghae Unit is returning home this week after 68 seamen tested positive for the coronavirus aboard a warship off the coast of Africa, the Joint Chiefs of Staff said Sunday. Two-thirds of the 301-strong crew are still awaiting test results.

This is the first time the military has cut short an overseas mission because of a pandemic. None of the seamen had received any COVID-19 vaccinations because the March vaccination campaign began a month after their departure.

“They’re coming back on aerial tankers we’re flying today,” a senior JCS official said. A fully vaccinated 148-strong Navy contingent backed by a medical team will be aboard the planes to take over the 4,400-ton destroyer Munmu the Great from the Cheonghae Unit.

The unit is expected to arrive home as early as Tuesday night, but it will take at least 40 days for Munmu the Great to sail back here. A second destroyer left here a month ago to replace the 4,400-ton destroyer as part of six-month rotational deployment. The takeover, which was to follow in August, was cut short.

Of the 68 COVID-19 patients, three were transferred to an undisclosed nearby hospital along with 12 others who have yet to get their COVID-19 test results but who complained of pneumonia symptoms. Three of those in the hospital -- one COVID-19 patient and two awaiting test results -- are moderately ill.

The outbreak is believed to have started July 2, a day after the destroyer left a nearby port where it had stopped for four days for supplies. A seaman exhibited cold symptoms and was treated with cold medicine but was not tested for the coronavirus.

On July 15, six patients were confirmed positive for the coronavirus. Many crew members exhibited cold or pneumonia symptoms.

The military, which suspects the virus spread to the ship from the local port, tested every service member aboard with help from Korean diplomatic missions nearby, but plans to test them again once they return home.

The military faces mounting criticism over the latest coronavirus outbreak, with critics accusing it of neglecting its responsibilities. The military could have shipped vaccines to the destroyer or found ways to inoculate the seamen, they said.

The military rebutted the criticism, saying that inoculating the crew onboard the warship would have been too risky because the medical staff would not have been equipped to treat anyone who had a severe allergic reaction to the vaccine and subsequently went into anaphylactic shock.

But that could be addressed with help from the nearby US Navy or local authorities, critics said.

About 72 percent of some 1,300 South Korean soldiers deployed overseas have received their COVID shots. But only 12 percent of the country’s 51 million population has been fully vaccinated due to supply constraints.