The U.S. Postal Service has become a critical backbone of the country’s medication infrastructure, meaning slowdowns in mail delivery could have serious consequences for the millions of Americans who get prescription drugs through the mail. Treatments for cancer, multiple sclerosis, rheumatoid arthritis and other complex diseases increasingly are sent in the mail. And the coronavirus pandemic has spurred more people to get their routine prescriptions mailed to their homes as a safer alternative to visiting a pharmacy. Americans received 313 million adjusted prescriptions through the mail in 2019, often for common, generic medications that treat things like high cholesterol and high blood pressure.