HOUSTON (AP) — Health departments around the U.S. that are using contact tracers to contain coronavirus outbreaks are scrambling to bolster their ranks amid a surge of cases and resistance to cooperation from those infected or exposed. With too few trained contact tracers to handle soaring caseloads, one hard-hit Arizona county is relying on National Guard members to pitch in. In Louisiana, people who have tested positive typically wait more than two days to respond to health officials — giving the disease crucial time to spread. Contact tracing tracks people who test positive and anyone they’ve come in contact with. It was challenging even when stay-at-home orders were in place, but it’s exponentially more difficult now.