The incidence of tuberculous infection in school children

Abstract

The percentage of reactors in the 42,000 children studied in this series shows a gradual trend upward from 21 per cent, infections at age 5, 28 per cent, at age 10 to 35 per cent, at age 15. The average percentage for the whole group is 28 per cent. Different sections in the same city may show a wide variation in the percentage of reactors. It was found in one city of 60,000 that the number of children reacting to the tuberculin test in different school districts varied from 11 per cent, to 60 per cent. The number of reactors increases with the opportunities that the child has for contact with bacilli carriers. Chronic forms of pulmonary tuberculosis, such as are found in granite quarry workers, expose and infect more children than the more acute cases, who live a much shorter time after the disease becomes infectious. Crowded living conditions afford more opportunities for contact and congested areas show a higher percentage of infection. Twice as many reactors are found among children with a history of direct contact with a case of pulmonary tuberculosis. Another factor to be taken into account is bovine infection. In a few rural towns with a scattered population and less than the average number of pulmonary tuberculosis deaths, we found as high as 38 per cent, reactors. The majority of the small towns, however, show a little less than the average percentage for the State as a whole. Susceptibility to infection appears to be equal in different nationalities. The tubercle bacillus infects the children of different nationalities to an equal degree when similar conditions for contact with carriers are present. The boys of the Irish, Canadian and Teuton groups in this series show a much higher incidence of infection than the girls, for which no explanation is offered. The tuberculin survey made in 1917 by the Framingham Demonstration and the one made in 1926 by the State Clinic for the same age group, 6 and 7 years, shows a reduction of 23 per cent. The children in the 1926 group averaged 5′7 years older than those examined in 1917, but the percentage of reactors was 8′5 per cent. less. While the numbers considered in this comparison are small, the marked reduction in infection checks up with the reduced death-rate in Massachusetts for all forms of tuberculosis, which declined from 144 per 100,000 in 1917 to 73 in 1927. Three important factors have operated to bring about a reduction in the number of infected children:— (1) The steady decline in the death-rate results in fewer persons with tuberculosis at large in the community to spread infection. (2) The State has a little more than one bed for each tuberculosis death in which to segregate cases of tuberculosis and so further reduce the foci of infection in the homes of these patients. (3) Pasteurized milk is now available for about 60 per cent, of the population of the State and by so much is the possibility of bovine infection curtailed. The efforts made in the past to eradicate tuberculosis from the herds in this State have been sporadic and therefore ineffective. The past year, however, a systematic plan for area testing has been put into effect, which promises better results. This plan deserves the hearty support of the public. The sources of tubercle bacilli, both human and bovine, being thus decreased, must result in fewer persons being exposed to infection. Therefore, we should expect to find a reduction in the number of reactors. Such indeed seems to be demonstrated by our survey. The tuberculin survey herein reported will afford a basis by which to measure the incidence of infection when comparable studies are made in future years. Tuberculous infection is no longer universal in Massachusetts. The increase in infection from five years to fifteen years averages one point per year. Granting that the same rate continued, the children now 15 years of age would show but 50 per cent, infection when 30 years old. A tuberculin test of a large, group of adults might show that to be the maximum percentage of infection even now. With the marked decrease in the number of infected persons, tuberculin tests become of diagnostic value in young adults, as well as in young children. If intracutaneous tests are made with increasing doses of tuberculin, beginning with 0·01 mg., then with 1 mg., and finally with 10 mg., without reaction, tuberculosis can be excluded in many persons suspected of having that disease. In such cases a negative test is of great value.