During Covid, how have we seen supply and demand in our healthcare system shift?When did we see shortages?

The U.S. shortage has multiple causes, including problems with the global supply chain. Before this pandemic, for instance, China produced approximately half the world's face masks. As the infection spread across China, their exports came to a halt. Now, as the infection spreads globally and transmission in China slows, China is shipping masks to other countries as part of goodwill packages. The United States has not been a major recipient.The shortages have led to pleas from individual U.S. health care providers trying to secure adequate supplies of PPE. The situation has become so dire that some providers are using social media and have even set up websites to obtain PPE directly. The Centers for Disease Control and Prevention (CDC) recommends that during crisis situations, N95 respirator masks be used only during aerosol-generating procedures, but that means risking exposure of health care workers using less protective surgical masks around patients with confirmed or suspected Covid-19 infection. Additional guidelines from the CDC include reusing masks and respirators intended for one-time use and, if stocks are fully depleted, using scarves or bandanas. The evidence to support these recommendations is thin.