COVID-19 activity is accelerating across the United States, according to the latest weekly update from the Centers for Disease Control and Prevention. The agency’s wastewater surveillance system—which can detect spread before clinical tests or hospital visits—has moved to a “moderate” alert nationwide, up from “low” the previous week. The West is driving the increase, with Alaska, California, Colorado, Nevada and Utah registering the highest viral concentrations. Separately, the CDC estimates infections are growing or likely growing in 45 states, up from 40 a week earlier. Although COVID-related emergency-room visits remain well below prior seasonal peaks, they have also risen over the past week, the agency said. Public-health officials say the uptick fits a pattern of summer surges that have become typical since the pandemic’s first year, but caution that vulnerable groups—including older adults, young children and the immunocompromised—should monitor local conditions and consider updated vaccinations and other preventive measures.