According to a study, the coronavirus may have spread through the ventilation system of an apartment complex in South Korea, where several residents of different households became infected.
The cluster was investigated after identifying a number of new cases of COVID-19 in August on several floors of the Seoul residential complex, according to the journal published in the International Journal of Infectious Diseases.
On August 23, a woman living on the sixth floor tested positive, followed by her husband and daughter.
The next day, a child living in the unit just below went to the hospital for a urological problem and also tested positive for the virus, the researchers wrote.
When another woman living directly below them on the fourth floor was diagnosed with COVID-19, health officials decided to test all 437 residents.
The investigators noted that the mother of the infected child also tested positive, along with two other residents living in units located directly above them on the 10th and 11th floors.
Two more cases were then found in other units on the second and eleventh floors of the tower.
These units are not directly above or below each other, but are in the same vertical line as each other and share the same ventilation system, the researchers said.
“All patients reported not knowing each other and denying a history of interpersonal contact,” the researchers wrote.
The researchers said the virus may have spread through shared spaces, such as elevators.
But they noted that all infected residents had reported wearing masks outside their apartments and that two had even refused to use the elevators.
They also noted that “among residents of more than 200 homes who can use the same elevators, all patients were only found on two vertical lines of the building.”
“Each line was connected through a single air duct to the bathroom for natural ventilation,” the researchers wrote.
“Our research found no other possible contact between cases where the infection was transmitted through the air through a single air duct in the bathroom.”
The researchers, however, point out that there were some limitations in the study, as they were unable to take air samples.
But the findings suggest that more research is needed on the potential risk.
“More people may have to stay indoors during the pandemic to avoid interpersonal contact,” the researchers concluded.
“However, some may be exposed to viral infection by inhalation due to inadequate ventilation systems.”