Transmission Classification Model To Determine Place and Time of Infection of Tuberculosis Cases in an Urban Area

Abstract

We conducted a population-based study in the Rotterdam region of The Netherlands to determine the place and time of infection of tuberculosis (TB) cases using conventional epidemiological and genotyping information. In particular, we focused on the extent of misclassification if genotyping was not combined with epidemiological information. Cases were divided into those with a unique mycobacterial DNA fingerprint, a clustering fingerprint, and an unknown fingerprint. We developed transmission classification trees for each category to determine whether patients were infected in a foreign country or recently (<2 years) or remotely (>2 years) infected in The Netherlands. Of all TB cases during the 12-year study period, 38% were infected in a foreign country, 36% resulted from recent transmission in The Netherlands, and 18% resulted from remote infection in The Netherlands, while in the remaining cases (9%) either the time or place of infection could not be determined. The conventional epidemiological data suggested that at least 29% of clustered cases were not part of recent chains of transmission. Cases with unknown fingerprints, almost all culture negative, relatively frequently had confirmed epidemiological links with a recent pulmonary TB case in The Netherlands and were more often identified by contact tracing. Our findings highlight the idea that genotyping should be combined with conventional epidemiological investigation to establish the place and time of infection of TB cases as accurately as possible. A standardized way of classifying TB into recently, remotely, and foreign-acquired disease provides indicators for surveillance and TB control program performance that can be used to decide on interventions and allocation of resources.The steady decline of tuberculosis (TB) incidence, especially since the introduction of chemotherapy in the 1950s, was reversed in the late 1980s in many developed countries due to immigration, concurrent human immunodeficiency virus (HIV) infections, and inadequate TB control practices (16). In the last 10 years, however, the general downward trend has resumed in many of these countries, necessitating review of current TB control strategies. Several countries where the incidence of TB is low are currently developing TB elimination plans in order to reach the goal of less than 1 case per million population per year (5, 22).For TB control, it is relevant to know where and when patients were infected, because recently infected patients represent ongoing transmission, those with remotely acquired infection are a result of TB transmission in the past, and patients infected in a foreign country are an expression of the particular TB situation in that country. The absolute TB incidence and the relative contributions of recently, remotely, and foreign-acquired disease influence the choice of TB control strategies (1,14,15). The proportion of recent transmission is also an important indicator for surveillance and TB control program performance (25,27).DNA fingerprinting of Mycobacterium...

Prevalence of and risk factors for active tuberculosis in migrants screened before entry to the UK: a population-based cross-sectional study

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Towards tuberculosis elimination: an action framework for low-incidence countries

“…A limiting factor for the impact of screening for active TB on transmission is that transmission rates are already very low in low-incidence countries. The majority of incident TB cases are generated through reactivation of LTBI acquired abroad or domestically in a distant past [ 61 , 123 – 125 ]. When transmission does occur, it is often in the form of limited outbreaks within the household, in healthcare facilities, or in congregate settings such as prisons or shelters, and more occasionally in pubs or schools [ 126 – 128 ].…”

Extent and origin of resistance to antituberculosis drugs in the Netherlands, 1993 to 2011

“…This resulted in the formation of 'clusters' with only one case left, which were excluded from further analysis. PDR cases were classified into three groups according to a classification model previously described [16]: (i) PDR cases with an M. tuberculosis strain that had a unique DNA fingerprint, as well as clustered cases without a potential source case (i.e. without a preceding pulmonary TB case in the cluster) were considered infected abroad or before 1993; (ii) clustered PDR cases with a potential source case, but without a confirmed or likely epidemiological link to a previous case in the cluster were considered possibly infected in the Netherlands; and (iii) clustered PDR cases with a potential source case and a confirmed or likely epidemiological link with a previous case in the cluster were considered definitely infected in the Netherlands.…”