How to build your own mask. You will need two ply of kitchen towels. Available in Dhaka in any grocery shop. Each roll at tk. 50.
But US still doesn't recommend face masks.
While Chinese authorities do.
Viruses ain't blocked by masks, but water droplets are. And viruses don't float in air by itself, it needs a carrier, and water droplets from breath and coughs are the carrier.
Just know that there are alternatives to buying masks at exorbitant price.