Original ResearchInvestigating tuberculosis trends in England
Introduction
The incidence of tuberculosis has been increasing in England since the late 1980s.1 Prior to this, tuberculosis numbers declined throughout the second half of the 20th Century, most likely due to a combination of factors including improved socio-economic conditions, and clinical and public health measures.2 The majority of cases of tuberculosis in the UK are now reported in the non-UK-born population, with rates of disease more than 20 times higher than in the UK-born population.3 In 1998, the proportion of tuberculosis patients estimated through record linkage to be co-infected with human immunodeficiency virus (HIV) was at least 3.3% in England and Wales.4 A number of studies in the UK have also looked at the relationship between tuberculosis and poverty, deprivation or social deprivation.5, 6, 7, 8, 9 Distinguishing the effects of deprivation from those of immigration or ethnicity has proved difficult.10 While some studies have found evidence of an association between the incidence of tuberculosis and socio-economic factors in the late 1980s,5, 6, 8 others have reported ethnic group as a stronger explanatory factor for variations in the incidence of tuberculosis.7, 9, 11
In Western Europe and the USA, a major factor in the increasing rates, or failure of the rates to decrease, over the last 20 years has been the migration of people from countries with a high incidence of tuberculosis.12, 13, 14, 15 This shift in the burden of tuberculosis in high-income countries from indigenous populations to mainly foreign-born populations has occurred during a global increase in tuberculosis incidence.16, 17 While factors such as poverty and overcrowding remain important root causes,18, 19 the main drivers of the recent global trend have been the HIV epidemic in sub-Saharan Africa and the collapse or neglect of control programmes and health systems in Eastern Europe and the former Soviet Union.20 A new concern in the latter and in the countries of South Asia is the impact of the growing HIV epidemic.21, 22 The contribution of HIV to the tuberculosis epidemic in Western Europe has been small15 and confined to specific populations or risk groups, such as injecting drug users or migrants from countries with high HIV prevalence rates.14 The number of people with HIV developing tuberculosis has also been affected by the advent of highly active antiretroviral therapy.23
The objective of this study was to investigate the factors associated with the increasing incidence of tuberculosis in England. Using national surveillance data from 1999 to 2003, the study examined the relationship between trends in the number of cases of tuberculosis over time and their demographic and clinical characteristics, including HIV co-infection and an ecological measure of deprivation.
Section snippets
Methods
National surveillance data on tuberculosis cases are collated annually by the Health Protection Agency, and are linked to results of drug-susceptibility testing of positive cultures from the mycobacterial reference laboratory network (MycobNet). Similarly, records in the national tuberculosis database for cases reported between 1999 and 2003 were linked with the national HIV/acquired immunodeficiency syndrome (AIDS) database to estimate the number of tuberculosis cases co-infected with HIV. All
Tuberculosis cases reported in England, 1999–2003
In total, 31,290 tuberculosis cases were reported between 1999 and 2003.∗ The median age was 37 years (interquartile range 26–57) and the male to female ratio of cases was 1.2:1. Thirty-nine percent (n = 11,404) of reported cases were from the Indian, Pakistani and Bangladeshi ethnic group, followed by 29% (n = 8431) from the White ethnic group and 19% (n = 5665) from the Black African ethnic group. Sixty-six percent (n = 17,987) of cases reported
Discussion
Analysis of national surveillance data shows that the number of cases and rates of tuberculosis increased significantly in England from 1999 to 2003. The most significant increases were observed in the number of cases in non-UK-born population groups, especially recent arrivals (arrival less than 5 years prior to diagnosis), the number of cases co-infected with HIV, and the number of cases from the Black African ethnic group. In London, there was a significant increase in the number of cases
Acknowledgements
The authors wish to thank David Quinn (database manager and data linkage design), Aliko Ahmed (HIV operator matching), Charlotte Anderson (MycobNet data management), Chris Lane (Geo Coding/Mapping work), Dr Jane Jones and Dr Michelle Kruijshaar (comments on manuscript). The authors are also grateful to the following professionals, without whose contribution national surveillance for tuberculosis would not be possible: tuberculosis nurses, chest physicians and microbiologists. Finally, the
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