The renewed surge in coronavirus cases across much of the U.S. is undermining efforts hospitals and manufacturers made in recent months to provide enough N95 masks to front-line workers.
Emergency responders and health-care workers from California to Florida are using more protective equipment and N95s—which block 95% of very small particles, including droplets containing the virus—as hospitalizations related to Covid-19 climb. At the same time, as restrictions on business have been lifted, factories and construction sites…