The Los Angeles County Department of Public Health has advised doctors to only test patients for the coronavirus if a positive result would actually impact their treatment. The department said in an official letter on Thursday that it was “shifting from a strategy of case containment to slowing disease transmission and averting excess morbidity and mortality.” The recommendation signaled a realization that there is little hope of containing the outbreak and came as a result of a growing number of patients and a limited number of tests. The decision could make it difficult to ever accurately determine the number of coronavirus cases in L.A. County, the country’s second-largest municipal health system.