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