Surveillance for bacillary dysentery in China, 2012

Objective To understand the epidemic pattern of bacillary dysentery and the serotypes as well as drug resistance of pathogens in China in 2012, and provide evidence for the prevention and control of the bacillary dysentery. Methods Descriptive epidemiological analysis was conducted on the surveillance data of bacillary dysentery collected from national disease reporting information system and national bacillary dysentery surveillance areas. Results In 2012, the morbidity of bacillary dysentery (15.29/lakh) decreased by 13.22% compared with 2011.The morbidity in people aged6 years and65 years was higher than the national average level. The cases in age group5 years accounted for 32.99% of the total. The morbidity was highest in age group1 year (215.02/lakh), followed by age group 1 year (99.83/lakh). The incidence of bacillary dysentery had obvious seasonality and the case number began to increase in April and peaked during June-September. A total of 12 bacillary dysentery outbreaks were reported in 2012, in which 11 occurred in school, 4 were waterborne outbreaks and 5 were foodborne outbreaks. Among 10 laboratory confirmed outbreaks, 8 were caused by Shigella sonnei (D group). The data from the 20 surveillance areas showed that the major pathogens were Shigella flexneri and Shigella sonnei, accounting for 69.93% and 30.07% respectively. S. flexneri 2a was most frequently isolated. No Shigella dysenteriae and Shigella boydii were isolated. The distribution of pathogens varied by areas. Most Shigella strains isolated were drug resistant and the drug resistance of the strains varied by areas too. Conclusion The morbidity of bacillary dysentery in China continued to decline in 2012. but the morbidity in children aged5 years, especially the infants less than 1 year old, was still high. Close attention should be paid to it. The prevention and control of bacillary dysentery still face serious challenge due to the development of pathogens' drug resistance and change of circulating strains.