Daily reports of new COVID-19 cases on the Diamond Princess cruise ship, quarantined near Yokohama with thousands trapped aboard, have raised a question: Why can’t Japan test all passengers at once?

According to the cruise operator, 2,666 passengers and 1,045 crew members were aboard the ship, which has been in Yokohama since Feb. 3 and has since been placed under a two-week quarantine. With the health ministry’s announcement Wednesday of an additional 39 confirmed cases on the ship, the total number of people infected aboard rose to 174. The tally for the domestic cases outside the ship is 29.

Health minister Katsunobu Kato said Wednesday his ministry will seek measures to screen everyone aboard the ship but Japan apparently has had its hands tied, as the number of test kits to diagnose the new coronavirus has been limited, in addition to logistics difficulties.

“We would be overrun,” Kato said during a news conference Monday when commenting on the stock of the kits.

A health ministry official confirmed Wednesday that only 492 samples have been collected so far, noting that the figure includes specimens collected from the same people multiple times.

The government’s response has raised the question of whether Japan has enough medical staff and adequate stock needed to perform diagnostic tests on all passengers.

“Tests kits enabling (quarantine officers) to verify results on the spot aren’t available now,” the official said.

He added that while the test methods used in Japan take four to six hours to deliver a result, “the problem lies in how to deliver the collected samples from the ship.”

Health laboratories check phlegm or throat swab samples from those on board, which are delivered to quarantine stations in Yokohama and other areas nationwide.

When asked about the delay in screening passengers, the ministry official cited logistics challenges.

The samples need to be sent within special leak-proof plastic tubes and wrapped in three layers. Only designated delivery companies are allowed to transport such infectious substances.

But the situation may improve soon, as Prime Minister Shinzo Abe on Wednesday said that the government will bolster testing capabilities to about 1,000 samples per day by Feb. 18 by allowing testing at private facilities, compared with up to 300 samples at the moment.

In screening for the virus, the government initially prioritized those with symptoms such as coughing and high fever and those who had been in close contact with such people. Subsequently, the elderly and those with pre-existing conditions were also given priority.

The ministry confirmed that four of the 174 people who have tested positive are in a serious condition, either on a ventilator or in an intensive care unit. Three of them are Japanese and one is non-Japanese, and all are in their 60s and 70s, according to the ministry.

The health ministry on Wednesday separately announced that one quarantine officer, who was dispatched to screen the cruise ship passengers between the evening of Feb. 3 and Feb. 4, also contracted the virus.

The ministry confirmed that the officer wasn’t wearing any protective uniform while on board the ship. The officer also spent another two days in a laboratory and was working without a mask, the ministry said. He tested positive on Monday but is in a stable condition.

In response to the outbreak, the World Health Organization has urged global leaders to boost diagnostic capabilities worldwide to combat the virus. The organization’s calls have prompted scientists around the world to develop test kits that would widen the network of facilities that can screen patients for the coronavirus.

Singapore’s Agency for Science, Technology and Research announced Sunday that it had developed and distributed to hospitals across the city-state a diagnostic kit that detects the presence of the novel coronavirus to tackle testing capacity problems. The agency is planning to deploy the kits to other hospitals and laboratories that are not offering COVID-19 tests.

A team of researchers at Hong Kong University of Science and Technology, meanwhile, claims it has invented the world’s fastest portable COVID-19 diagnostic device, which can detect the virus in just 40 minutes. Samples are taken from the nasal cavity, which are then put into the analyzer for testing.

These test kits aren’t available in Japan.

The quarantine on the Diamond Princess, which is docked at Daikoku Pier Cruise Port in Yokohama, will not be lifted until Feb. 19 at the earliest. But some government officials have reportedly said that passengers who have not shown symptoms should be released to prevent the virus from spreading within the ship.

But once the passengers are released, they won’t necessarily be free to go sightseeing.

“Those who have been exposed to the virus, for instance people who stayed in the same room as any of those who have contracted the virus, may need to be tested once again,” the health ministry official said. The official added that if they test positive, they may be put under quarantine again.

RELATED PHOTOS Relatives of passengers watch the Diamond Princess as it sails from Daikoku Pier Cruise Terminal in Yokohama on Tuesday to spend a day at sea dumping wastewater and generating drinking water. | AFP-JIJI