Last week the American fashion industry went dark as stores and factories closed, both voluntarily and by government decree, to help prevent the spread of the new coronavirus.

Yet by the weekend, lights had flicked on again on both coasts as designers and manufacturers began to pivot from making dresses, jeans and bathing suits to making surgical face masks and other protective gear — even as President Donald Trump addressed the US, saying unspecified help would be on the way for hospitals that expect to be overwhelmed and under-resourced.