Tuberculosis primary infection

Since the introduction of mass BCG vaccination program, it has become difficult to know how TB primary infection takes place. Based on data before the introduction of mass BCG vaccination, the author tried to overview TB primary infection. Most TB primary infection takes place via lung as shown in Table 1. Soon after TB primary infection, primary focus in the lung and regional glandular changes were formed, and they were named primary complex, which is the morphological sign of TB primary infection. Comparing the location of primary focus in right and left lung, it was 56.6% vs. 43.4%, which just correspond to the right and left lung volume as shown in Table 2. Observing by the location of primary focus in different lung lobes, it was found more frequently in upper lobe than in middle and lower lobe after adjustment for volume of different lung lobes as shown in Fig. 1 and Table 2, however, chronic pulmonary TB is found much more frequently in apex or upper part of the lung. The number of primary foci was 1 in the majority of cases, however, 2 or more foci were found in some cases. Several weeks after TB primary infection, TB immunity started to work, and primary focus be never formed thereafter. The fact indicates that multiple primary foci were seen only repeated TB infection taking place in short period soon after primary infection. The distribution of number of primary foci should follow Poisson's distribution if repeated infection takes place by chance, and it should follow Polya-Eggenberger's distribution if chance of repeated infection takes place cumulatively, and observed figure matched with the latter as shown in Fig. 2. Location of primary complex is useful sign to determine invasion place of tubercle bacilli in epidemiological survey of TB infection in medical accident cases. If major pulmonary lesions are found in middle or lower part of lung, we have to suspect onset of TB soon after primary infection among immunity attenuated cases such as HIV/AIDS, diabetics and cases using steroid, and if cavities are found more likely diabetes is suspected, and no cavity with or without adenopathy more likely HIV/AIDS.