If, as seems likely to me, like this:

[![Woolly aphid][1]][1]
(*Image courtesy Tmaq97*)

They are [Eriosomatinae](https://en.wikipedia.org/wiki/Eriosomatinae) (woolly aphids] rather than [whiteflies]( https://en.wikipedia.org/wiki/Whitefly). They can be [dealt with](https://www.rhs.org.uk/advice/profile?pid=181) fairly easily. Those that don’t just wash off can be sprayed with 'horticultural' soap (that is, not a detergent) and, where available, neem oil.

These insects fly/are blown around in the atmosphere. Your plants should be salvageable and I'd not bother with a mesh or moving indoors. Depending on where you are more sunlight may be better overall and a mesh might do more to keep out  their predators than the aphids.  


  [1]: https://i.sstatic.net/enKlo.jpg