[Recent case-finding activities of school children in Japan]

The procedure for TB mass-screening of elementary and junior-high school students was revised in 2003 in Japan. An interview sheet with questions about the past history of TB, episodes of contact with TB patient, TB symptoms, and BCG vaccination history has been administered to all students to determine high-risk groups for TB infection or TB disease despite previous mass-screening with PPD testing for those in first grade. Our purpose in the present study was to evaluate the effects of revised case-finding activity for these school students.

We analyzed the case-finding activities for school students from 2003-2008 based on data from the national TB surveillance system and related ad-hoc surveys.

The total number of notified TB cases among these students was 295 out of which 156 were detected by contact survey, 110 by consultation at medical facilities with symptoms, 19 by mass-screening at schools, and the remaining 10 by other means. Although the contact investigation detected more than half of all cases, there were some more cases with a known source of infection among those who were detected in other modes; 28 cases were identified by consultation at medical facilities and 10 by school mass-screening. Case-finding activities by consultation at medical facilities detected 43 bacteriologically positive cases. There were 97 cases without a known source of infection. Most of the cases detected by school mass-examination had risk factors such as TB history in the family and/or a history of staying in TB-prevalent countries. The TB incidence in urban areas is higher than that in other areas for junior-high school students with known or unknown sources of infection.

The effectiveness of the contact investigation could be enhanced by improving its way of implementation. Delay of diagnosis for infectious cases should be minimized as much as possible to prevent TB outbreaks among students. For that purpose, parents, school teachers, and school nurses should be aware to prevent a delay in seeking care for the patient. Because the efficiency of the current school mass-screening is quite low, revision of this program is necessary, taking into consideration the reinforcement of other case-finding activities. The difference between urban and other areas might be due to a higher infection risk in junior-high school students in urban areas who have higher social activity and may be exposed to higher TB infection risk due to casual contact.