Saline nasal irrigation and gargling for the common cold (2019)

"A church in South Korea sprayed salt water inside the mouths of followers out of a false belief it would help prevent the spread of the coronavirus, but by using the same spray bottle without disinfecting the nozzle, it resulted in 46 church-goers infected, authorities said on Monday."

https://www.scmp.com/week-asia/health-environment/article/30...

Also see https://www.nature.com/articles/s41598-018-31936-y

These articles suggest saline water might actually be effective against coronaviruses and similar viruses, contrary to what WHO suggests.