As worried citizens scramble for facial protection to ward off Covid-19, an underground market of substandard surgical masks has flourished overnight in the national capital and its neighbourhoods, an Aajtak investigation has found. The supplies, the probe discovered, are produced in extremely unhygienic and unsafe conditions, rendering them vulnerable to infection. Health experts world over have warned that Covid-19 spreads through respiratory droplets and also possibly through surfaces and objects that have the virus on them.