Lifting the mask on tuberculosis : distribution of notified cases in Stockholm County 1989 to 1996

Sammanfattning: In order to investigate the distribution and burden of tuberculosis (TB) in Stockholm County during the period 1989 to 1996, a descriptive study was conducted. The TB cases registered in the central TB register during that period were studied.  Demographic profiles, geographic distribution, disease presentation and diagnosis of registered TB cases were described. During 1989 to 1996, 1022 TB cases were registered in Stockholm County accounting for 23% (1022/4487) of all TB cases in Sweden during that period.  The crude annual incidence was stable, oscillating between 7,1 and 8,1 per 100 000 population. Stratification by national origin showed a decrease of the annual incidence from 4,3 to 3,3 cases per 100 000 in the Swedish born population and an increase from 149,4 to 238,9 among the Africa borns. The overall age distribution of 1022 cases showed a bimodal pattern, peaking among young adults aged 25 to 44 years and among the elderly above 64 years. Stratification by age showed a declining trend in the age group above 64 years. In this age group the proportion of Swedish born was 85%. An increasing trend was observed in the age group 18 to 24 years. In this age group 91% were foreign born. The median age declined from 61 years during 1989 to 37 during 1996. The average annual incidence varied in the different municipalities between 1,3 (Ekerö) and 10,7 (Sundbyberg)per 100 000 population. The highest average annual incidence was found in Spånga parish. Due to an increased number of Africa born TB cases, the annual incidence in Spånga increased three-fold from 18,1 to 48,0 per 100 000 population. Nearly two-thirds (63) of the cases had pulmonary TB, 16% had lymphatic TB and 21 % had other extra –pulmonary lesions. The site of disease showed gender and ethnic differences. Lymphatic TB was more common in females, while pulmonary and other extra- pulmonary TB were more common in males. The highest proportion (42%) of lymphatic TB was found among Asian female cases compared to 4% in the Swedish male cases. Crude county incidence does not reveal geographic and ethnic clustering of TB cases. Clinical manifestations of TB vary depending on sex and ethnic differences. As being a low-incidence county, Sweden could be well suitable for TB eradication. To achieve such goal, the national TB control program need to be restructured in order to facilitate cluster oriented interventions.