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In Taiwan, although the coverage rate of two doses of measles-containing vaccine has been maintained at over 95% since 2001, measles outbreaks occurred in 2002, 2009, and 2011. The present study reports that 43 cases were confirmed by laboratory testing in Taiwan in 2012-2014 and that adults have emerged as one of groups susceptible to measles virus (MV) infection, who may have discrepant humoral immune reactions--indicated by the level of IgM and IgG antibodies compared to a naive, susceptible measles case. Thirty-seven of 43 cases confirmed by RT-PCR were further characterized by genotyping. In Taiwan, genotype H1 was the major strain in circulation prior to 2010, while D9 was the most frequently detected MV genotype between 2010 and 2011. The genotyping data collected between 2012 and 2014 revealed that H1 rebounded in 2012 after an absence in 2011 and was imported from China and Vietnam. In 2014, genotype B3 first appeared in Taiwan following import from the Philippines and became the most frequently detected strain. Genotype D8, linked to importation from various countries, including India, Indonesia, Thailand, and Vietnam, showed sequence divergence. D9 was imported from Malaysia in 2014. The MV genotypes detected in Taiwan reflected the genotypes of circulating endemic measles strains in neighboring countries. A significant rise in the number of measles cases and in measles with genotypes imported from surrounding countries indicated that measles resurged in Asia in 2014.

Rubella has been listed as a mandatory notifiable disease in Taiwan since 1988. Because of high coverage rates with an effective vaccine, rubella cases have decreased dramatically in Taiwan since 1994. However, rubella outbreaks still occur due to imported transmission. Five large clusters were detected in Taiwan from 2007 to 2011. In 2007, one cluster was caused by rubella genotype 1E viruses that were imported from Vietnam, whereas another cluster was caused by genotype 2B viruses and was untraceable. In 2008, two clusters were caused by different lineages of genotype 1E viruses that were imported from Malaysia. In 2009, a cluster that was caused by genotype 2B viruses was associated with imported cases from Vietnam. The rubella viruses from 124 confirmed cases from 2005 to 2011 were characterized, and the data revealed that these viruses were distributed in the following four genotypes: 1E (n = 56), 1h (n = 1), 1j (n = 4), and 2B (n = 63). Of these viruses, 93 (75%) were associated with imported cases, and 43 of 56 genotype 1E viruses were associated with imported cases from China, Vietnam, Malaysia, and Indonesia. One genotype 1h virus was imported from Belarus, and three of four genotype 1j viruses were imported from the Philippines. Of 63 rubella genotype 2B viruses, 46 were imported from Vietnam, Thailand, Malaysia, China, Germany, and South Africa. Molecular surveillance allows for the differentiation of circulating rubella viruses and can be used to investigate transmission pathways, which are important to identify the interruption of endemic virus transmission. J. Med. Virol. 85:745–753, 2013. © 2013 Wiley Periodicals, Inc.

In Taiwan, although the coverage rate of two doses of measles-containing vaccine has been maintained at over 95% since 2001, measles outbreaks occurred in 2002, 2009, and 2011. The present study reports that 43 cases were confirmed by laboratory testing in Taiwan in 2012-2014 and that adults have emerged as one of groups susceptible to measles virus (MV) infection, who may have discrepant humoral immune reactions--indicated by the level of IgM and IgG antibodies compared to a naïve, susceptible measles case. Thirty-seven of 43 cases confirmed by RT-PCR were further characterized by genotyping. In Taiwan, genotype H1 was the major strain in circulation prior to 2010, while D9 was the most frequently detected MV genotype between 2010 and 2011. The genotyping data collected between 2012 and 2014 revealed that H1 rebounded in 2012 after an absence in 2011 and was imported from China and Vietnam. In 2014, genotype B3 first appeared in Taiwan following import from the Philippines and became the most frequently detected strain. Genotype D8, linked to importation from various countries, including India, Indonesia, Thailand, and Vietnam, showed sequence divergence. D9 was imported from Malaysia in 2014. The MV genotypes detected in Taiwan reflected the genotypes of circulating endemic measles strains in neighboring countries. A significant rise in the number of measles cases and in measles with genotypes imported from surrounding countries indicated that measles resurged in Asia in 2014.

Measles has been controlled effectively in some countries because of high coverage rates with an effective vaccine. However, measles outbreaks still occasionally occur in areas with high vaccine coverage as a result of imported transmission. To identify the sources of measles infection and to determine whether measles cases are part of a single outbreak or due to multiple importations, measles virus (MV) genotyping is required and plays an important role in MV elimination. In Taiwan, genotype H1 of MV was detected most frequently before 2009. From 2006 to 2011, 47 of 48 genotype H1 cases were associated with the imported cases, indicating that genotype H1 was not an endemic genotype in Taiwan after 2006. The distribution of the other genotypes (D3, D4, D5, D8, D9, and G3) detected during 2006-2011 varied by year. Taiwan has a pattern of measles genotypes that is consistent with the elimination of MV and with the absence of endemic genotypes. In this study, the genotypes of 40 cases of MV detected during 2010-2011 were investigated and analyzed. In 2010, the most common genotype changed from H1 (3/40) to D9 (35/40). In 2011, genotype H1 was not detected, and genotype D4 first appeared and was imported from Europe. The dynamic change of detected genotypes of MV in Taiwan is influenced by the activity of a measles control program in WHO regions. This study emphasizes that global synchronous elimination is important for an individual country or area to maintain free from MV.