Measles outbreaks in the post-elimination era in the Americas

Background: In the Americas, endemic transmission of indigenous measles virus was interrupted in November 2002. However, sporadic cases and outbreaks associated with importations continue to occur.

Methods: Data from an integrated measles-rubella surveillance system and from country specific reports was analyzed to describe recent measles outbreaks in Brazil and Venezuela in 2006-2007.

Results: In November 2006, Brazil reported a measles outbreak, concentrated in 5 municipalities of Bahía State. The majority (68%) of the 57 confirmed cases were men, with individuals >15 years at highest risk. None of the cases had vaccination history. The last case occurred in epidemiological week (EW) 47, 2006 and the measles genotype identified was D4, which has been isolated in Europe, Africa, and Asia.

Between February 2006 and February 2007, Venezuela reported a total of 118 confirmed measles cases. The outbreak began in the States of Caracas, Carabobo, Nueva Esparta, and Zulia, following an importation from Spain (B3 genotype), and continued in Guárico and Amazonas States. The rash onset of the last confirmed case was 15 February 2007.

Discussion: High population immunity must be ensured to maintain the interruption of indigenous measles transmission and prevent large outbreaks following importations. Lessons learned through outbreak investigation and response in the region include, 1) maintaining high coverage with routine measles-containing vaccine to protect new cohorts, 2) completing mass vaccination campaigns with MR vaccine and continuing periodic follow-up campaigns, striving to attain >95% coverage, 3) ensuring high-quality integrated measles/rubella surveillance, and 4) developing country contingency plans to respond to outbreaks.