An outbreak of Salmonella Paratyphi A in a boarding school: a community-acquired enteric fever and carriage investigation.

Salmonella Paratyphi A (SPA) is rapidly becoming a common cause of enteric fever in South East Asia. A large outbreak of SPA occurred in a boarding middle school in China in 2004. There were 394 suspected cases; 95·5% were students. The highest incidence was in the youngest children (7th grade). Forty-four of 151 (29%) blood cultures and 4/54 (7·4%) rectal swabs were positive for SPA; three were from kitchen workers. The geometric mean levels of serum IgG anti-lipopolysaccharide (anti-LPS) from patients was higher than from healthy individuals [35·25 vs. 5·20 ELISA units (EU), P<0·001]. A kitchen worker with a positive rectal swab, negative blood culture and a high level of serum IgG anti-LPS (529·65 EU), was identified as a possible SPA carrier. No SPA was isolated from water or food samples. A survey of students' habits indicated drinking unboiled water as being the main reason for contracting the disease. Hand washing was the second most important factor. A food handler with possible SPA carriage could also have been a risk factor. Attention to maintaining a safe water supply, enhancing food-handler hygiene and proper hand washing can help to prevent similar outbreaks in the future.