Abstract
BackgroundThe number of scarlet fever occurrences reported between 2000 and 2006 fluctuated considerably in central Taiwan and throughout the nation. Isolates of Streptococcus pyogenes were collected from scarlet fever patients in central Taiwan and were characterized by emm sequencing and a standardized pulsed-field gel electrophoresis (PFGE) method. National weekly report data were collected for investigating epidemiological trends.ResultsA total of 23 emm types were identified in 1,218 S. pyogenes isolates. The five most prevalent emm types were emm12 (50.4%), emm4 (23.2%), emm1 (16.4%), emm6 (3.8%) and emm22 (3.0%). PFGE analysis with SmaI suggested that, with a few exceptions, strains with a common emm type belonged to the same clone. There were two large emm12 clones, one with DNA resistant to cleavage by SmaI. Each prevalent emm clone had major PFGE strain(s) and many minor strains. Most of the minor strains emerged in the population and disappeared soon after. Even some major strains remained prevalent for only 2–3 years before declining. The large fluctuation of scarlet fever cases between 2000 and 2006 was associated with the shuffling of six prevalent emm clones. In 2003, the dramatic drop in scarlet fever cases in central Taiwan and throughout the whole country was associated with the occurrence of a severe acute respiratory syndrome (SARS) outbreak that occurred between late-February and mid-June in Taiwan.ConclusionThe occurrences of scarlet fever in central Taiwan in 2000–2006 were primarily caused by five emm types, which accounted for 96.8% of the isolates collected. Most of the S. pyogenes strains (as defined by PFGE genotypes) emerged and lasted for only a few years. The fluctuation in the number of scarlet fever cases during the seven years can be primarily attributed to the shuffling of six prevalent emm clones and to the SARS outbreak in 2003.
Highlights
The number of scarlet fever occurrences reported between 2000 and 2006 fluctuated considerably in central Taiwan and throughout the nation
Epidemiological trend of scarlet fever Taiwan is an island country populated by 22.9 million people, most of whom reside in the western region (Figure 1A)
In our previous work on 179 S. pyogenes isolates collected in central Taiwan between 1996 and 1999, the five most common emm types in central Taiwan remained the same, but the frequency changed in the two time periods, 1996– 1999 and 2000–2006 [7]
Summary
The number of scarlet fever occurrences reported between 2000 and 2006 fluctuated considerably in central Taiwan and throughout the nation. Streptococcus pyogenes (Group A streptococcus) is a common pathogen responsible for a number of human suppurative infections, including pharyngitis, impetigo, pyoderma, erysipelas, cellulitis, necrotizing fasciitis, toxic streptococcal syndrome, scarlet fever, septicemia, pneumonia and meningitis. It causes non-suppurative sequelae, including acute rheumatic fever, acute glomerulonephritis and acute arthritis [1]. Scarlet fever, characterized by a sore throat, skin rash and strawberry tongue, is most prevalent in school children aged four to seven years old. Scarlet fever outbreaks frequently occur in young children at day-care centers, kindergartens and elementary schools [2,3] and occur in adults upon exposure to contaminated food [4]
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