Is scarlet fever—long thought to be eradicated—reemerging as a health threat? China, the United Kingdom, and Hong Kong have seen upsurges in scarlet fever cases in the past few years.
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Hong Kong has seen a more than 10-fold increase over the previous incidence rate. In a study of 7,266 patients aged ≤ 14 years (3,304 with laboratory-confirmed diagnosis), researchers from University of Hong Kong found a “sharp peak” in 2011: 1,438 cases were reported, exceeding the total number of 1,117 in the previous 6 years. Since then, the annual number of reported cases has remained at a “relatively high level,” the researchers say, with an average of 14.5 cases per 10,000 children during 2012-2015.
The elevated pattern was more apparent in children aged ≤ 5 years. In that age group, annual incidence averaged 3.3 per 10,000 during 2005-2010, then jumped dramatically to 23.9 per 10,000 in 2011. It dropped slightly to 18.1 per 10,000 in 2012-2015.
The cause is unclear, the researchers say. They cite 1 report that suggests toxin acquisition and multidrug resistance may have contributed. School is probably a major transmission site. Incidence was higher among younger children entering school and during school days. The researchers say boys were more at risk than girls, possibly because they have more physical interactions or poorer personal hygiene. Thus, school-based control measures—especially for boys aged 3 to 5 years—could be “particularly important.”