The Diamond Princess cruise ship lockdown began after an 80-year-old passenger who spent five days on the ocean liner tested positive for coronavirus – sparking fears that he brought the virus on board.
The elderly Hong Kong passenger boarded the vessel in Yokohama on January 20 after flying out to Japan.
On January 22 he took part in a bus trip with other passengers in Kagoshima, Japan, before the ship sailed to Hong Kong where he left on January 25.
In his five days on the cruise liner he did not report any problems to the ship’s on-board medics, but six days after leaving he went to hospital in Hong Kong.
On February 1 he tested positive for coronavirus, prompting Japanese authorities to deny entry to the ship and screen more than 3,700 people for the virus when the vessel returned to Yokohama on February 3.
Of the 3,711 people screened on the ship, 273 were selected for further tests. They had disembarked in Hong Kong or been in contact with the 80-year-old.
It is not yet known for certain whether the 80-year-old was the cruise ship’s ‘patient zero’ who transmitted the virus to other passengers.
The deadly virus could have been brought on board by another person as American passengers Clyde and Renee Smith said they had been on a bus trip with the man in Kagoshima but both tested negative for the virus.
Guests who had been in contact with him were among the 273 selected for testing, of whom 61 since tested positive.
Japanese media said the man had been in contact with 36 passengers, including at least two of the first ten who tested positive.
Medics are not yet sure how the coronavirus spreads, but similar infections are passed on through droplets when people cough or sneeze.
When the 80-year-old man tested positive, tour operator Princess Cruises said the relatives he was travelling with did not show any symptoms of the virus.
On February 3 he was said to be in a stable condition in hospital. There has been no update on his condition since then.
An American couple, Clyde and Renee Smith, said they had been on a bus trip with the man in Kagoshima but both tested negative for the virus.
‘While on the ship he did not visit the ship’s medical centre to report any symptoms or illness,’ the cruise operator told passengers earlier this week.
After he left the ship, it sailed to Vietnam and then to Taiwan on January 31 where 16 cases of the new coronavirus have been confirmed.
Taiwanese media said it was unclear how many passengers left the ship at the port of Keelung, sparking an alternative theory that the virus could have been transmitted there.
After leaving Taiwan, the ship continued to the Japanese island of Okinawa before arriving back in Yokohama on February 3.
Japanese authorities immediately quarantined the ship while the 2,666 passengers and 1,045 crew members were screened for the virus.
Since then, medics in hazmat suits have gone deck-to-deck to test selected passengers while other guests were ordered to remain in their cabins.
The 61 people found to have been infected with the virus have been moved to hospitals on the Japanese mainland to be kept in quarantine.
Remaining passengers face nearly two more weeks in lockdown, with the quarantine set to continue until February 19.
The ship has spent much of its time anchored in Yokohama Bay, where fork lift drivers in hazmat suits have helped to load supplies on to the vessel.
It has also returned to the open sea to collect seawater, which can be converted for use in showers and drinking water.
Experts say that cruise ships are particularly vulnerable because of the large number of passengers, many of them older people, in a confined space.
Outbreaks of droplet spread diseases such as influenza and norovirus are relatively common’ on such ships, said Professor Paul Hunter, a medical researcher at the University of East Anglia.
‘Cruise ships often have large numbers of passengers and crew, these people come from all over the world, and passengers at least are often elderly,’ he said.
‘Given that many passengers spend a large part of their time indoors, one would expect droplet spread diseases such as [the new virus]to spread readily on board.
‘As passengers will disperse back around the world then outbreaks on board such ships will have the potential to enhance the global spread of this current epidemic.’
Professor William Keevil of the University of Southampton said some passengers may be unwilling to come forward with their symptoms to avoid putting an expensive holiday at risk.
The environmental healthcare specialist said keeping guests in their cabins was the ‘best option’ until the incubation period – thought to be around 14 days – has passed.
Crews are ‘well aware of the spread of disease on board, considering that you can have hundreds or thousands of passengers in a relatively confined, isolated environment for days or weeks,’ he said.
‘They rely on the honesty of the passengers declaring if they are unwell or have had a recent illness as they board ship.
‘The problem is that some potentially ill passengers, having looked forward to their holiday and spent a lot of money, do not want to miss out and board ship anyway.’