Trends in importation of measles to the United States, 1986-1994
C. R. Vitek, S. C. Redd, S. B. Redd and S. C. Hadler
Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. cxv3@cdc.gov
OBJECTIVES: To describe patterns among imported measles cases to the United
States. DESIGN: Descriptive analysis of national case-based surveillance
data on measles cases. SETTING: United States in the period 1986 through
1994. PATIENTS: All reported confirmed cases of measles. MAIN OUTCOME
MEASURES: Demographic variables, immunization history, country of exposure,
and reporting state. RESULTS: The number of reported imported cases of
measles to the United States has dropped from an average of 99 cases
annually in 1986 through 1988 and 190 cases in 1989 through 1991 to 61
cases in 1992 through 1994. Since 1990, the number of imported cases
originating in Latin America declined by 98%, despite continued increase in
the number of travelers to this region; cases from other regions remained
relatively constant. This decrease paralleled the rapid decrease in measles
incidence in the Western Hemisphere associated with national measles
elimination programs. Most imported cases occurred among children, although
22% of cases occurred among young adults. Rates of measles cases per 1
million travelers are higher among non-US citizens than among US citizens.
CONCLUSIONS: The sharp decline in importations into the United States from
Latin America since 1991 provides evidence of the success of measles
control efforts undertaken there. The decrease in imported cases has been
associated with a decline in total measles cases in the United States.
Sustained elimination of measles in the United States will require improved
measles control in other countries in addition to a high level of
population immunity.
