Epidemiological Investigation of a Shigellosis Outbreak At a Mental Institution in Taoyuan County
1999 Vol.15 NO.7
Shigella is the main infectious agent of Shigellosis. Estimate is that, worldwide, excluding the mainland China, around 140 million children under five years are infected each year, causing 576,000 deaths(14). Serotypes S. sonnei and S. flexneri are common in Taiwan. S. flexneri is found more often in outbreaks at mental institutions or nursing homes; whereas S. sonnei is seen more often in schools or communities through contaminated underground water(24,25) . An outbreak of dysentery at a mental institution was reported in September 1998, the climax being on 15 September. Laboratory testing of rectal swabs collected from patients with symptoms confirmed that the incident was S. flexneri infection. In May 1997, the institution had a similar Shigellosis infection. This outbreak should be the second infection. An epidemiological investigation was conducted immediately to understand the mode of transmission and the risk factors. The overall attack rate was 28.1%. No clustering by room was noticed. Residual chlorine in water for hand washing at the toilet was zeros. The common source of the outbreak was considered to be the contaminated underground water.