In the good old days the topic was called Public Health, nowadays its called Plumbing and Drainage. It is essential for all buildings to have properly designed, installed and maintained sewerage systems to prevent infecting occupants, whether it is 2003 SARS, 2020 COVID19, or Influenza.
youtube is unreliable here is the link: https://www.youtube.com/watch?v=Uv38qdl4Z1M
Recently, when COVID19 infection was discovered spreading within Hong Mei House, Tsing Yi on 10 and 11 February 2020, the RTHK report stated that the HK Government instantly reported it was not a “U trap” problem [RTHK link] a reference to the SARS outbreak in 2003 where the disease spread through the drainage system in block E Amoy Gardens infecting occupants, and requiring evacuation of the block.
youtube is unreliable at the moment, here is the link https://www.youtube.com/watch?v=GTNvTuV_CM4
I predicted the cause would be the sewer vent pipe, vent pipes are part of the high rise drainage system designed to prevent loss of the water seal in U traps. Subsequently, my suspicion was confirmed, the SMCP newspaper confirmed that the vent piping inside the bathroom was damaged (see SCMP photo below). Therefore, droplets could contaminate the bathroom area.
Still problems in 2020
The photo below taken 15 March 2020 shows damaged drainage system vent piping.
That drainage system is damaged, it is no longer an enclosed system, allowing odour, bacteria, virus to escape into the air.
We have always known that sewerage and drainage systems are important, providing a conduit for bacteria and viruses, yet the severe lessons from SARS in 2003 and now from COVID19, demonstrate lessons still have not been learned!