Epidemiologic Investigation into an Outbreak of Typhoid Fever Recognized by Electronic Data Interchange in Gyeongsangbuk-do, 2003

Lim, Hyun Sul; Min, Young Sun; Lee, Kwan; Lim, Sang Hyuk

Abstract

Epidemiologic Investigation into an Outbreak of Typhoid Fever Recognized by Electronic Data Interchange in Gyeongsangbuk-do, 2003 PURPOSE: Fourteen cases of typhoid fever occurred in Gyeongsan-si, Gyeongsangbuk-do from May 22 to July 19, 2003. Especially, 6 cases were students of Y University located in Gyeongsan-si. This investigation was carried out to study the infection source and transmission of typhoid fever and to institute an effective prevention counterplan.
METHODS
The authors conducted an epidemiologic survey from June 25, 2003 among the 14 cases, restaurants and employees of the whole neighborhood of Y University. Widal test was carried out for the restaurant employees and schoolmates of the 13-year-old case Miss Kim. The authors executed a pulsed field gel electrophoresis (PFGE) for Salmonella typhi cultured from 9 cases. The authors collected data about chloride and turbid levels of treated water from April to June in Gyeongsan-si water treatment plant and repair work records of waterworks pipe line in Gyeongsan-si city hall.
RESULTS
All cases had used restaurants of the whole neighborhood of Y University within 2 months before the typhoid fever symptoms were developed, but the restaurant that was rarely visited by any of the patients had a case to be matched. In the results of the Widal test, 9 out of 45 of subjects (20.0%) were suspicious cases or showed a value to suggest past infection. In the results of PFGE test, there were 3 subtypes, and each subtype had a similar DNA fragments array. In all cases the patients drank tap water when they visited the restaurants. The restaurants provided drinking water from filtered tap water rather than boiled water, and all patients had drunk this water. The chlorine level of the treated water was the normal value in the Gyeongsan-si water treatment plant, but in 2 times the value was the minimum standard level. There was water pipe construction work in some regions of the whole neighborhood of Y University. The number of gastrointestinal patients in 2003 was approximately 2 times that in 2002 at the health center in Y University.
CONCLUSIONS
The possibility that typhoid fever was generated in the whole neighborhood of Y University is very high. Among various possibilities, the highest possibility is the pollution of tap water intake by water leakage of a water pipe. There was no case of patient infection after strengthening of the tap water disinfection. Thorough disinfection, boiled drinking water and a periodic carrier inspection are necessary to prevent additional local occurrences of these typhoid infections.