U.S. Coronavirus Cases Dropped Dramatically Since January, But Can We Keep Them Down? By Will Stone February 26, 2021 Updated 2:12 p.m. ET With coronavirus infections on a steady, six weeks long descent in the U.S., it’s clear the worst days of the brutal winter surge have waned. Yet researchers are still not sure how sustainable the decline is. And a small but concerning uptick in cases in the last three days has health officials on edge. So what caused the massive decline since January, and what can the U.S. do to ensure that it lasts? New infections have fallen close to 70% nationwide in just over six weeks, bringing the average number of cases to levels last seen in early fall.