—from Epidemiological Bulletin, Vol. 24 No. 1, March 2003—

Absence of Transmission of the D9 Measles Virus in the Region of the Americas,
November 2002 - May 2003

In line with the goal set in 1994 by countries of the Americas to interrupt indigenous measles transmission, as of 14 May 2003, the Region has been free for 24 weeks from known indigenous circulation of the D9 measles virus, the strain responsible for the only large outbreak of measles in the region during 2002.

The measles vaccination strategy recommended by the Pan American Health Organization (PAHO) includes a one-time, national “catch-up” campaign for all children 1 to 14 years of age, routine “keep-up” vaccination for infants aged 1 year, and national “follow-up” campaigns every 3 to 4 years for all children 1 to 4 years of age, regardless of measles vaccination history. Rapid house-to-house monitoring for local validation of vaccination activities and active epidemiologic and virologic surveillance are also important parts of the strategy.

During 1997-2001, reported confirmed measles cases in the Region of the Americas decreased 99%, from 53,683 in 1997 to 541 in 2001. Although the transmission of the D6 measles virus genotype was interrupted in September 2001, that same month the D9 genotype was introduced into Venezuela by a traveler returning from Europe. The resulting outbreak included 2,501 cases in Venezuela and 140 cases in Colombia; however vaccination efforts by both countries stopped further transmission of the virus. As of 14 May 2003, no circulation of the D9 virus has been reported for 24 weeks.

Progress toward interruption of indigenous measles transmission in the Region of the Americas reflects sustained high political commitment by member countries and full implementation of PAHO’s recommended measles-control strategies and suggests that global measles eradication is achievable. However, important challenges remain. Measles is still endemic in other regions, and sporadic cases continue to occur in the Region of the Americas because of importation. The majority of countries in the region have not achieved and sustained routine measles vaccination coverage rates of >95% in all municipalities. Because poor, underserved neighborhoods in large cities that attract migrants of rural origin are particularly at risk for measles outbreaks when the virus is reintroduced, persons living in these areas are targeted for supplementary vaccination activities.

Source: PAHO's Area of Family and Community Health, Immunization Unit, as published in: Public Health Dispatch: Absence of Transmission of the d9 Measles Virus - Region of the Americas, November 2002 - March 2003. MMWR 2003; 52(11):228-229.

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Epidemiological Bulletin, Vol. 24 No. 1, March 2003