Figure. . Trends in scarlet fever during outbreak in Hong Kong, Guangdong, and Macau, People’s Republic of China, 2011. A) Monthly scarlet fever notifications in Hong Kong, Guangdong (data obtained from Department of Health Guangdong Province, www.gdwst.gov.cn/a/yiqingxx), and Macau (data obtained from Health Bureau, Government of the Macau Special Administrative Region (www.ssm.gov.mo/news/content/ch/1005/statistic.aspx). Vertical tick marks indicate January of each year. Data from Guangdong and Macau were available beginning in 2005. Black line indicates data from Hong Kong; gray line, data from Guangdong; broken line, data from Macau; gray bar, number of imported cases in Hong Kong, 2005-2011. B) Weekly notifications of scarlet fever cases in Hong Kong and monthly notifications in Guangdong and Macau. Black line indicates data from Hong Kong; gray line, data from Guangdong; broken line, data from Macau. C) Estimated instantaneous reproduction number (Rt) and 95% pointwise confidence intervals (CIs) based on scarlet fever notifications in Hong Kong, February–December, 2011. Black line indicates estimate calculated by grouping patients with unknown importation status with patients with imported cases; gray line, estimate calculated by grouping patients with unknown importation status with local case-patients; broken lines, the upper and lower limits of the 95% CIs for Rt. For better presentation, CIs are shown only for the former estimates. Horizontal line indicates the critical value of Rt, under which transmission of disease will not be sustainable.