According to an article published in SFGate, a new, unpublished study of data collected during the COVID-19 outbreak on the Diamond Princess cruise ship in February suggests that the virus likely spread through the ship’s air-conditioning system.
The analysis, which has not been peer-reviewed, was distributed by the health preprint server MedRxiv on Thursday.
Cabin Comparison Revealed The Truth
rsity and King’s College London looked at symptomatic infection rates during the quarantine period in cabins with previous confirmed cases and compared them to those in cabins without previous confirmed cases, including those in single-occupancy rooms.
The expectation was that the rate of infection would be significantly higher in the cabins that had confirmed cases (passengers who tested positive and were taken into isolation off the ship). But the results showed that was not the case.
The scientists concluded that airborne transmission of COVID-19 through the ship’s ventilation system could explain how the virus spread into cabins.
- By Feb. 20, 619 COVID-19-positive cases — of which 301 were symptomatic — were confirmed on the ship.
- A total of 163 of those, 115 passengers and 48 crew, recorded symptom onset during the quarantine period Feb. 6-17.
- The analysis showed that 20% of those 115 passenger cases occurred in cabins that had previously had a passenger with a confirmed, symptomatic COVID-19 infection staying in it.
- Eighty percent were in cabins that didn’t have a previous confirmed case.
Close Contact in Ship Cabins Spreads Corona
“It is not possible to infer exactly when all cases on Diamond Princess were infected due to the variance in COVID-19 incubation periods among individuals and to the lack of symptom presentation in many cases,” the study’s authors Orouba Almilaji and Peter W. Thomas wrote. “However, we assume that … the infection risk is higher when there is a close contact with a sick person within a small space such as ships’ cabins.”
The study found that age distributions among the cabins did not appear to make a difference in the results.
Role of ventilation
The role of ventilation systems in facilitating COVID-19 infections has come under increasing scrutiny as the pandemic spreads. At a restaurant in Guangzhou, China, an outbreak involving three family clusters in late January and early February was linked the airflow of the establishment’s air-conditioning system.
Another study confirmed that speech droplets can linger in the air for tens of minutes. Droplets from infected individuals could transmit the disease in confined spaces and via ventilation systems.
- The Diamond Princess HVAC (heating, ventilation and air-conditioning) system is similar to those in found in many restaurants, hospitals, nursing homes, gyms, buses and trains, office buildings, prisons and schools.
- The ship does not have higher ventilation rate and high-efficiency particulate air (HEPA) filters that effectively reduce airborne transmission of pathogens on airplanes.
“The design of the air conditioning system in the Diamond Princess shows that air from different passengers’ cabins gathered in one
air duct, mixed with some fresh air (30% only) and then [was] re-supplied to the different cabins again,” the study’s authors wrote.
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