X-axis labels are week/month, from the 44th week of 2001 (in November) to the 9th week of 2002 (in February). The blue line shows the number of cases per week reporting to an EWORS site in Jakarta with watery diarrhea and dehydration, fever, or vomiting. The “Cusum” (cumulative sum) C1, C2, and C3 alerts identify, with increasing sensitivity, significant increases in case counts using the Early Aberration Reporting System []. The horizontal red solid and broken lines represent the long-term mean and mean plus two standard deviations (sometimes used as an outbreak detection threshold in other surveillance systems), respectively.