What is the Sharia ruling on the suggestion of thoroughly washing the hands with water and soap before rinsing the mouth (madmadah), sniffing water into the nose (istinshaq), and washing the face during wudu, as a preventative measure against the transmission of viruses, and can this be generalized to people?

The important thing is for a Muslim to perform ablution (Wudu') as Allah has commanded. Washing hands with water and soap before ablution is permissible, whether for preventing illness or for other reasons. There is no need to actively promote it, as health organizations have already guided people to do so. Striving for prevention with moderation is commendable, while exaggeration is blameworthy.