Measles surveillance in five major US cities: Chicago, Houston, Los Angeles, Miami, and New York.

Endemic measles, if it occurs in the United States, will likely be found in cities, because large populations are required to sustain transmission and importations of measles virus are most frequent in cities. We investigated measles surveillance systems in 5 cities (Chicago, Houston, Los Angeles, Miami, New York City) during 1995-1999. The passive reporting of a measles case activated the systems to look for more cases and to intervene to prevent more cases. During 1995-1999, 1363 suspected measles cases were investigated. Only 58 of these were confirmed as measles (0.24 cases/100000 people), and the majority (57%) of confirmed cases were imported or linked to an importation. Most (83%) suspected cases that met the case definition had a complete case investigation, including a laboratory test for measles. We conclude that surveillance in these 5 cities shows no evidence of endemic measles transmission.