As I explained a couple of weeks ago, it seems plausible that the 2019 Coronavirus (now officially designated as Covid-19) may spread e.g. vertically through a building of flats via the various piping systems. This is based on a theory of what happened in a cluster of SARS cases in Hong Kong in 2003.

CNN and others are discussing this today after officials in Hong Kong partially evacuated a building where this is again a possibility.