TOKYO—All but a handful of the passengers of the disease-stricken Diamond Princess cruise ship berthed in Yokohama have disembarked. But for Japan, the saga is far from over. Much of the crew remains on board, enduring another 14 days of quarantine—although this time under conditions that Japanese officials hope will prevent any additional infections.
But there has been another worrisome development: As of today, eight public servants who worked on the ship to support the quarantine have tested positive for COVID-19, and more may follow. Most of the roughly 90 health ministry employees who visited the ship during the first 2-week quarantine that ended on 19 February initially returned to their normal work duties, but in light of the infections, the health ministry yesterday revised its policy and now those potentially exposed to the virus on the Diamond Princess are self-quarantining at home for 14 days, according to a ministry official who asked not to be identified.
Still, there are fears here that Japan’s handling of the crisis may lead to new chains of infection. There are now 700 confirmed COVID-19 cases linked to the Diamond Princess, not counting infections discovered among passengers after they’ve gone home. The U.S. Centers for Disease Control and Prevention reports that 36 American Diamond Princess passengers who returned on emergency flights have been confirmed as carrying the virus.
Aside from the cruise ship, as of noon yesterday Japan has identified 144 cases, including among people repatriated from Wuhan, China. The total, 844, means Japan ranks second, just behind South Korea, in the number of confirmed cases outside mainland China.
The 2-week quarantine, which trapped more than 3700 people under increasingly hazardous conditions, has come under fierce criticism. Last week, Kentaro Iwata, an infection control specialist at Kobe University, posted a scathing video about the conditions on board, which he said were “violating all infection control principles.” Japanese bureaucrats and medical personnel visited the ship to tend to passengers, conduct epidemiological surveys, and coordinate arrangements to move people to hospitals or to chartered flights home. The fact that so many became infected “really confirms Professor Iwata’s concerns,” says Paul Hunter, an infectious disease epidemiologist at University of East Anglia.
Normally, those supporting a quarantine don’t have to be quarantined themselves, presuming they use personal protection equipment (PPE)—masks, gloves, goggles, and gowns. “But the available evidence suggests that PPE was not appropriately used on board,” Hunter says. He believes the officers who worked onboard the Diamond Princess should have been quarantined once the problems with infection control came to light. If such lax management had resulted in the infection of government officials in the United Kingdom, “I suspect criminal proceedings would follow,” Hunter says.
The staged release of passengers from 19 to 23 February has triggered worries as well. One Japanese passenger who tested negative when disembarking returned to her home 100 kilometers or more away in Tochigi prefecture by train and tested positive during a follow-up examination on 22 February. In response, the health ministry will increase passenger health checks, health minister Katsunobu Kato said during several weekend press conferences here. He also confirmed that 23 people had disembarked the ship and gone home without being tested for the virus. The ministry is now tracking them down for testing.
Another big concern is that among many of the cases unrelated to the Diamond Princess clear routes of transmission have not been identified, Kato said. Over the past 2 weeks, people sickened by COVID-19 have been popping up in widely disparate locations with no identifiable source. Whoever infected those people may have infected many others as well.
The transmission chain becomes invisible, completely off our radar.
“This is a very tricky virus,” says Hitoshi Oshitani, a virologist and public health specialist at Tohoku University. It’s clear that some infected people are transmitting the virus before recognizing symptoms and perhaps never even realizing they were infected with COVID-19. “The transmission chain becomes invisible, completely off our radar,” Oshitani says. “We’re not seeing a suddenly increasing number of cases, we are just seeing a suddenly increasing number of detected cases.”
South Korea is also seeing a rapid expansion of cases, as are Iran and Italy, which experts say makes it increasingly unlikely that the virus can be stopped altogether. Instead, the Japanese strategy “is to slow the speed of the expansion” of the outbreak, Shigeru Omi, a public health specialist who heads the Japan Community Health Care Organization, said at a press briefing here last week. Hopefully this will reduce the overall number of infections and delay the peak of the outbreak, buying time to strengthen health care capabilities, said Omi, who was previously the World Health Organization’s western Pacific regional director. He added that early detection of and high-quality care for severe cases will hopefully cut mortality rates.