To the Editor: Strebel and Orenstein (July 25 issue)(1) discuss several complications of measles infection, including subacute sclerosing panencephalitis. The frequency of this complication is often, and perhaps inevitably, underestimated as a result of inadequate diagnosis and reporting.(2) Previous reports calculated a risk of 1 per 25,000 to 45,000 measles cases in the general population and 1 per 2000 to 5500 measles cases among children younger than 1 year of age.(3,4) However, in a more recent review of cases in California in the period 1998-2015, Wendorf et al. found an incidence of subacute sclerosing panencephalitis according to the time of . . .