Update, February 20:
The last handful of more than 300 people were set to be released to return home on Wednesday afternoon. More than 2,200 people remained quarantined after the ship, MS Ushio, docked in Japan on Monday.
The outbreak is being investigated and authorities are working hard to find all the cases.
More than 900 passengers and crew were infected by the norovirus after being exposed to passengers or crew on board the Triumph.
Speaking at a press conference on Wednesday morning, Morimoto said about 429 individuals, mostly non-Japanese nationals, had tested positive. More than 200 people who were sickened have fully recovered, while 175 are showing slight symptoms.
Coronavirus outbreak feared to be growing in Japan after cruise ship docked on Monday. Read: pic.twitter.com/Rd52InP6ZJ — BBC News (World) () February 20, 2019
Norovirus can make many people violently ill within 24 hours of exposure, and has become increasingly common among cruise ship passengers. Most infections can be managed with oral antiviral medications.
The cruise line that the MS Ushio, a registered Greek ship, left Singapore on Monday remained quarantined Wednesday after all of its 1,998 passengers and crew members tested positive for the virus. No new cases have emerged. The ship was found to have mixed with more than 3,300 other passengers at anchor near the port city of Ushio on the west coast of Japan.
Oman’s public health ministry said that the virus had been found on 106 people including crew members, but had yet to reach authorities in Japan. An investigation into the ship is underway and will determine who may have contracted the virus.
It is unclear how the virus, which is said to be highly contagious and can be transmitted in water, was allowed to leave the vessel. It is also unclear if the cruise was a related event to other outbreaks of the virus in the Pacific, such as in Hawaii and Canada.
The island of Tahiti is one of the most frequently attacked spots by norovirus. In 2015, nearly 2,500 people were infected by the virus in just a few days. The virus was also found in Guatemala in 2018 and is one of several pathogens that have spiked in outbreaks in recent years.
This post has been updated to reflect new information.
About 600 children sent home from Carnival cruise ship in Hawaii with gastrointestinal illness
400 people sickened by norovirus aboard Carnival ship in Hawaii