Incidence, risk factors relating to bacillary tuberculosis and secondary infections from registered patients in Hunai-Gun, Kyoto Prefecture

Abstract

To review how to strengthen tuberculosis program in Hunai-Gun, Kyoto Prefecture, the recent trend of incidence of tuberculosis and 148 index cases with pulmonary tuberculosis newly registered from 1987 to 1992 were analyzed regarding the mode of detection, conditions when consulting medical facilities, risk factors, bacteriological findings, and secondary infections among contacts. 1. The high crude incidence of tuberculosis in Hunai-Gun is explained by the high proportion (19.3%) of the elderly population of 65 years old and over in Hunai-Gun compared with the average (12.6%) in the Prefecture and the high tuberculosis incidence among age group of 70 years old and over in Hunai-Gun compared with the prefectural average. However, the reason of higher incidence of tuberculosis among the elderly in the district was not clear. 2. The proportion of bacillary as well as culture positive cases were higher among patients who were diagnosed by consulting medical facilities than those detected by regular health check. The proportion of bacillary cases without risk factors for tuberculosis among patients who were diagnosed at medical facilities was the highest among those newly attending medical facilities due to complaints related to tuberculosis (group A), followed by those patients regularly attending medical facilities for other diseases but consulting because of additional complaints related to tuberculosis (group B), and lowest among patients regularly attending medical facilities but detected by chance while being examined for other diseases (group C). The severer the diseases stage, the higher the proportion of bacillary cases, however, there were no difference in the proportion of bacillary cases among the above three groups including those with risk factors. It is explained by the fact that the ratio of patients with risk factors was high in group C, which masked the higher proportion of bacillary cases among patients with risk factors. 3. As future activities of public health center on tuberculosis control, it is important to give health education to those with risk factors on the fact that the progression of the disease is faster among them in addition to the increased risk of the disease onset, and advise them to attend regular health check and visit medical facilities when they have any symptom related to tuberculosis. 4. Considering the fact that the risk of secondary infection to contacts is higher among smear positive patients than bacilli negative patients, it is needed to examine all contacts of sputum smear positive patients thoroughly. In addition, it is advisable to follow-up contacts of smear negative but culture positive patients with the similar intensity with those for smear positive patients because their risk of secondary infection to contacts was also higher than bacilli negative patients although it was not statistically significant.