Reported annual measles cases worldwide declined by almost 40 percent between 1990 and 1999. Nonetheless, an estimated 30 million to 40 million cases occurred in 2000, resulting in approximately 777,000 deaths (WHO and UNICEF, 2001). Measles accounts for nearly half of the 1.7 million annual deaths due to childhood vaccine-preventable diseases. In 1999, the African continent accounted for 58 percent of all estimated measles cases in the world, 87 percent of which were located in the west and central regions (WHO, 2000g). In southern Africa, the number of reported measles cases decreased from over 50,000 annually to 100 in 1999 because of intensive vaccination campaigns (WHO, 2002k). In the Americas, countries that have adequately implemented the strategies recommended by the Pan American Health Organization/WHO have successfully inhibited measles transmission.
The number of reported cases in the United States plummeted from approximately 500,000 before vaccine introduction in 1963 to fewer than 1,500 in 1983 (Bellini and Rota, 1998). Despite these measures, however, a resurgence of measles occurred in the United States between 1989 and 1991, causing more than 55,000 cases and approximately 120 measles-associated deaths. Most of the cases occurred in children under 5 years of age. Of those who lost their lives during this epidemic, 90 percent had not been vaccinated (CDC, 2001k). As a result of successful vaccination efforts, the number of reported measles cases dropped to less than 100 in 2000 (CDC, 2002p). Although it was announced in 2000 that measles was no longer endemic in the United States (CDC, 2002q), a continued risk remains for internationally imported measles cases that could result in indigenous transmission.
Diphtheria had been well controlled in Russia for two decades following the initiation of a universal childhood immunization program in the late 1950s. In the 1970s, however, the number of cases began to rise (see Figure 3-9). The epidemic of diphtheria in the Newly Independent States of the former Soviet Union in the early 1990s marked the first large-scale diphtheria epidemic in industrialized countries in three decades (Vitek and Wharton, 1998). In 1993, the number of reported diphtheria cases surged to nearly 20,000, occurring primarily throughout urban Russia, the Ukraine, Belarus, and the Baltics. By 1994, the number of reported diphtheria cases had surged to 50,412 in the Newly Independent States, with Russia accounting for 83 percent of the cases. In 1994, epidemic diphtheria was reported for