When we last checked in on the city’s outbreak of the rare virus, it consisted of 20 cases concentrated in northern Manhattan and the Bronx. (One was found in Brooklyn.) Now the Health Department has announced that five new measles patients — including three on the Lower East Side — have been identified in the last three weeks. Though officials seem to think that the outbreak may have begun at a medical facility, they have yet to identify its exact source. In the meantime, they are still urging people to vaccinate their children, which, in case you haven’t heard, is not something everyone does these days.