A study by the Centers for Disease Control and Prevention found that emergency room visits nationwide fell 42% in April, from a mean of 2.1 million a week to 1.2 million, compared with the same time period in 2019. At Hoag Memorial Hospital Presbyterian in Newport Beach, California, mammograms have dropped as much as 90% during the pandemic. “When you see only 10% of possible patients, you’re not going to spot that woman with early-stage breast cancer who needs a follow-up biopsy,” said Dr. Burton Eisenberg, executive medical director of the Hoag Family Cancer Institute.