Molecular epidemiology of tuberculosis in London 1995-7 showing low rate of active transmission

Abstract

Background: Tuberculosis notification rates for London have risen dramatically in recent years. Molecular typing of Mycobacterium tuberculosis has contributed to our understanding of the epidemiology of tuberculosis throughout the world. This study aimed to assess the degree of recent transmission of M tuberculosis in London and subpopulations of the community with high rates of recent transmission. Methods: M tuberculosis isolates from all persons from Greater London diagnosed with culture positive tuberculosis between 1 July 1995 and 31 December 1997 were genetically fingerprinted using IS6110 restriction fragment length polymorphism (RFLP) typing. A structured proforma was used during record review of cases of culture confirmed tuberculosis. Cluster analysis was performed and risk factors for clustering were examined in a univariate analysis followed by a logistic regression analysis with membership of a cluster as the outcome variable. Results: RFLP patterns were obtained for 2042 isolates with more than four copies of IS6110; 463 (22.7%) belonged to 169 molecular clusters, which ranged in size from two (65% of clusters) to 12 persons. The estimated rate of recent transmission was 14.4%. Young age (0-19 years) (odds ratio (OR) 2.65, 95% confidence interval (CI) 1.59 to 4.44), birth in the UK (OR 1.55, 95% CI 1.04 to 2.03), black Caribbean ethnic group (OR 2.19, 95% CI 1.15 to 4.16), alcohol dependence (OR 2.33, 95% CI 1.46 to 3.72), and streptomycin resistance (OR 1.82, 95% CI 1.15 to 2.88) were independently associated with an increased risk of clustering. Conclusions: Tuberculosis in London is largely caused by reactivation or importation of infection by recent immigrants. Newly acquired infection is also common among people with recognised risk factors. Preventative interventions and early diagnosis of immigrants from areas with a high incidence of tuberculosis, together with thorough contact tracing and monitoring of treatment outcome among all cases of tuberculosis (especially in groups at higher risk of recent infection), remains most important.

Explaining risk factors for drug-resistant tuberculosis in England and Wales: contribution of primary and secondary drug resistance

“…However, this is probably less important in the United Kingdom where recent transmission is relatively infrequent [26]. Our findings suggest that the pathways to drugresistant disease are not simple and, for some risk factors, change over time.…”

Analysis of Changes in Recent Tuberculosis Transmission Patterns after a Sharp Increase in Immigration

“…Our molecular epidemiology study showed that foreignborn people were much less likely to be in the clustered group, and this could mean a higher percentage of infection before arriving in Spain. As the percentage of reported TB cases among foreign-born people continues to grow, the control of TB in Madrid will depend increasingly on TB case findings, tracing the contacts, and screening people at high risk for infection among this population (7,10,20).…”

A systematic review of rapid diagnostic tests for the detection of tuberculosis infection

“…13 TB in London is largely caused by reactivation or importation of infection by recent immigrants. 14 In 2003, the mortality rate from TB in England and Wales was around 0.74 per 100,000 population, varying from under 2% for children and young adults to over 30% in those aged 65 years or over. 13 The rates of new infections have been increased by the marked rise in international travel, by the breakdown of public health measures in some of the Eastern European countries and by increases in the number of people with impaired immunity following the spread of HIV infection.…”