Residents living in units 09 on every floor of Oi Fai House in Yau Oi Estate were sent into quarantine.
Three of coronavirus cases are residents of that unit on the 21st to the 23rd floors. The fourth infection lives in a different flat on the 22nd floor, and experts believe she had picked up the bug in a different way.
After inspecting the building, University of Hong Kong microbiologist Yuen Kwok-yung noted that one of the flats had two exhaust fans in the kitchen, and the flat was apparently modified so the room was directly linked to the toilet.
Yuen, one of the government’s advisors on the pandemic, said the exhaust fans may have sucked the virus in after creating negative pressure in the room.
The expert said while it appears that the virus travelled downwards, there’s no definitive proof of this, so authorities decided to evacuate all residents who live in the same units on every floor as a precaution.