Is that entire apartment buildings were getting infected, a case on the first floor would infect folks on the 7th. It turns out a lot of landlords made unauthorized changes in their buildings and the work was shoddy and the sewer fumes were spreading the virus throughout the building.
Below is just a taste of the issue.
https://thehill.com/changing-america/well-being/prevention-cures/482798-can-coronavirus-spread-through-pipes-officialsEdited by Da_Haze at 22:36:13 on 04/21/20