Evaluation of hepatitis A surveillance data and outbreak detection in Yunnan Province, China, from 2004 through 2009.

Hepatitis A outbreaks may be averted if detected early. The current study objectives were to evaluate the quality and timeliness of hepatitis A surveillance data from Yunnan Province, China, and to evaluate the sensitivity of the system for reporting outbreaks. The study period was from January 1, 2004 through December 31, 2009. Records from the National Infectious Diseases Surveillance System (NIDSS) were compared with those from local hospitals. The timeliness of case detecting, reporting and updating was also analyzed. The numbers of cases in a specific location during a moving time interval were computed to identify past outbreaks which were then validated against reported cases. The NIDSS received 38,095 reports during the study period; of which 6% were duplicates, and 26% had serological confirmation. The sensitivity and positive predictive value of cases were 96% and 98%, respectively. Time from onset to diagnosis remained constant over the 6-year period. Delays in reporting became shorter, and quality control of data improved over the period, but the timeliness of identifying duplicate records did not. Based on data from NIDSS, 9 outbreaks should have been reported, but only 3 were reported. The 3 reported outbreaks were shorter in duration than the 6 unreported ones, but the numbers of cases involved were not significantly different. Surveillance data needs improvement in updating timeliness. The system for outbreak detection and reporting needs to be improved.