It comes during an already bleak year for the nation’s public health: The number of measles cases hit a 34-year high this summer, largely driven by the so-called “Southwest outbreak,” which grew to more than 880 cases across Texas, New Mexico and Oklahoma. Several epidemiologists agreed that the current scale and spread of cases most closely resembles the large outbreaks of the early 1990s — before nationwide immunization campaigns and school vaccine mandates helped the United States declare the virus eliminated.