Being purists, the CDC is not calling the current upswing in measles cases an “outbreak”—defined as three cases in an area within a month—but any “reasonable person” would likely do so.
In 2000, we said that measles had been eliminated in the U.S. In 2016, there were 86 cases, and in 2017, 118 cases. The year is only half over, yet we already have 107 cases across 21 states and D.C., including eight clusters that meet the CDC definition.