Changing trends and serotype distribution of Shigella species in Beijing from 1994 to 2010

Mao, Yuanli; Cui, Enbo; Bao, Chunmei; Liu, Zhenhong; Chen, Suming; Zhang, Juling; Wang, Huan; Zhang, Chenglong; Zou, Jing; Klena, John D; Zhu, Baoli; Qu, Fen; Wang, Zhiyun

A statistically significant decreasing trend in S. flexneri and an increasing trend in S. sonnei were observed by chi-square analysis (p < 0.01) ( Figure 1 ). The trends in Shigella spp. isolated from Beijing between 1994 and 2010 are shown in Figure 2 . The recording of annual Shigella isolation began in 1994, and the maximum number of isolates was reported in 1996 (n = 1194). The annual total number of isolated Shigella organisms had been decreasing since then, reaching a low point in 2008 (n = 22). This trend may be related to the strict hygiene inspection and adequate sanitation during the 2008 Olympic season [17] . Four peaks were observed during the 17-year collection period. Peak 1 appeared in 1996, with subsequent peaks in 1998 (peak 2, n = 602), 2002 (peak 3, n = 398), and 2004 (peak 4, n = 251). A sudden decrease in Shigella isolation was observed more in 2003 than in 2002 and 2004; one possible explanation is that resources were redirected to identify severe acute respiratory syndrome cases in China in 2003, thereby limiting bacterial diarrheal isolation. It should be noted that as the numbers of observed cases of shigellosis were decreasing, China's per capita gross domestic product (GDP) was increasing ( Figure 3 ).