A Century of Tuberculosis Epidemiology in the Northern and Southern Hemisphere: The Differential Impact of Control Interventions

Background
Cape Town has one of the highest TB burdens of any city in the world. In 1900 the City of Cape Town, New York City and London had high mortality of tuberculosis (TB). Throughout the 20th century contemporaneous public health measures including screening, diagnosis and treatment were implemented in all three settings. Mandatory notification of TB and vital status enabled comparison of disease burden trajectories.
Methods
TB mortality, notification and case fatality rates were calculated from 1912 to 2012 using annual TB notifications, TB death certifications and population estimates. Notification rates were stratified by age and in Cape Town by HIV status (from 2009 onwards).
Results
Pre-chemotherapy, TB mortality and notification rates declined steadily in New York and London but remained high in Cape Town. Following introduction of combination chemotherapy, mean annual case fatality dropped from 45–60% to below 10% in all three settings. Mortality and notification rates subsequently declined, although Cape Town notifications did not decline as far as those in New York or London and returned to pre-chemotherapy levels by 1980. The proportional contribution of childhood TB diminished in New York and London but remained high in Cape Town. The advent of the Cape Town HIV-epidemic in the 1990s was associated with a further two-fold increase in incidence. In 2012, notification rates among HIV-negatives remained at pre-chemotherapy levels.
Conclusions
TB control was achieved in New York and London but failed in Cape Town. The TB disease burden trajectories started diverging before the availability of combination chemotherapy in 1952 and further diverged following the HIV epidemic in 1990. Chemotherapy impacted case fatality but not transmission, evidenced by on-going high childhood TB rates. Currently endemic TB results from high on-going transmission, which has been exacerbated by the HIV epidemic. TB control will require reducing transmission, which is inexorably linked to prevailing socio-economic factors.

背景
开普敦是全球结核病（Tuberculosis，TB）负担最为沉重的城市之一。1900年，开普敦市、纽约市与伦敦均出现了极高的结核病死亡率。整个20世纪期间，三地同步推行了涵盖筛查、诊断与治疗的公共卫生干预措施。结核病强制上报与生命状态登记制度，为比较三地的疾病负担演变轨迹提供了可行条件。

方法
本研究基于1912年至2012年的年度结核病上报数据、结核病死亡证明及人口估算数据，计算了三地的结核病死亡率、上报率与病例病死率。上报率按年龄分层，其中开普敦地区自2009年起新增按HIV（Human Immunodeficiency Virus）感染状态进行分层统计。

结果
化疗问世前，纽约与伦敦的结核病死亡率及上报率呈稳步下降态势，但开普敦的相关指标仍维持高位。联合化疗方案引入后，三地的年均病例病死率均从45%~60%降至10%以下。此后三地的死亡率与上报率均有所回落，但开普敦的上报降幅不及纽约与伦敦，至1980年已回升至化疗前水平。纽约与伦敦的儿童结核病占比逐渐降低，但开普敦的儿童结核病占比仍处于高位。20世纪90年代，开普敦暴发HIV疫情，这与结核病发病率进一步翻倍密切相关。2012年，HIV阴性人群的结核病上报率仍维持在化疗前水平。

结论
纽约与伦敦已成功实现结核病防控，但开普敦的防控工作宣告失败。三地的结核病负担演变轨迹早在1952年联合化疗普及前便已出现分化，1990年HIV疫情暴发后，这种分化进一步加剧。化疗仅对病例病死率产生影响，并未改变结核病的传播态势，这一点可从持续高企的儿童结核病发病率得到印证。当前结核病流行源于持续的高水平传播，而HIV疫情进一步加剧了这一状况。结核病防控需以减少传播为核心，而这与当下的社会经济因素密不可分。