Two new studies looking at COVID-19 cases from the Diamond Princess Cruise ship have provided new information about how the virus spreads and the symptoms many people experience when infected.
The Princess Cruises ship was the location of one of the first major outbreaks of the SARS-CoV2 coronavirus outside of China after and was quarantined at Yokohama port in Japan for over a month. Over 700 passengers and crew from the 3,700 on board were ultimately infected after a single passenger from a previous cruise tested positive after disembarking she ship in early February. Of the 712 people infected on board, eight so far are known to have died, according to the Johns Hopkins coronavirus tracker and experts have been widely critical of the quarantine and containment approaches used by the Japanese government.
The ship became a floating laboratory for studying the spread of the coronavirus in confined spaces and predictably, scientists are now using this data to try and learn about how the coronavirus spreads and affects people in the rest of the world.
A new report from the Japanese CDC gives more details about the COVID-19 cases among the crew members on board the ship and provides vital information about how the virus is transmitted. For example, eight of twenty crew members with confirmed COVID-19 shared their cabins with another crew member. Of these eight cabin mates, five went on to also develop COVID-19, providing further evidence that the virus spreads quickly among those living near to one another. This trend was also reflected with those living close by on the same deck, with 16 out of the 20 affected crew members living on deck 3. 15 of the 20 affected staff also worked in the same department, preparing food for their fellow crew members.
“This investigation underscores the need for swift epidemiologic investigation as soon as a COVID-19 case is detected in an area or group where a large number of persons gather in a closed or crowded setting (e.g., a cruise ship, music club, health care setting, sports arena, or gymnasium),” – Japanese CDC report, 17th March 2020.
As Forbes contributor Bruce Y. Lee explains here, the scientists were also able to estimate that 17.9% of people infected on the ship had shown no symptoms, a vitally important piece of information to influence how public health authorities around the world respond to the virus in their own backyards.
The second study looked at computerized tomography (CT) scans taken from 112 people who had contracted confirmed COVID-19 on board the Diamond Princess with an average age of 62, although the ages ranged from 25 to 93 years old. Of the 112 people scanned, 73% of them didn’t have any clinically obvious symptoms but half of these people had detectable changes in their lungs indicating some level of pneumonia. Of the 27% of people who did show COVID-19 symptoms, 4 out of 5 people showed abnormal CT findings.
“We investigated the chest CT findings in laboratory-confirmed COVID-19 cases in an environmentally homogenous cohort of cruise ship passengers and crew members, comparing the CT characteristics of asymptomatic and symptomatic cases,” said the study authors in a statement. “Noticeably, we found lung parenchymal changes on CT in up to 54% of the asymptomatic cases,” they added.
The studies provide further evidence that people can be carrying the virus but not actually be noticeably sick, a big problem for containing the outbreak and further reason for people to practice social distancing even when they are not experiencing any symptoms.