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      Space-Time Clustering Characteristics of Tuberculosis in China, 2005-2011


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          China is one of the 22 tuberculosis (TB) high-burden countries in the world. As TB is a major public health problem in China, spatial analysis could be applied to detect geographic distribution of TB clusters for targeted intervention on TB epidemics.


          Spatial analysis was applied for detecting TB clusters on county-based TB notification data in the national notifiable infectious disease case reporting surveillance system from 2005 to 2011. Two indicators of TB epidemic were used including new sputum smear-positive (SS+) notification rate and total TB notification rate. Global Moran’s I by ArcGIS was used to assess whether TB clustering and its trend were significant. SaTScan software that used the retrospective space-time analysis and Possion probability model was utilized to identify geographic areas and time period of potential clusters with notification rates on county-level from 2005 to 2011.


          Two indicators of TB notification had presented significant spatial autocorrelation globally each year ( p<0.01). Global Moran’s I of total TB notification rate had positive trend as time went by ( t=6.87, p<0.01). The most likely clusters of two indicators had similar spatial distribution and size in the south-central regions of China from 2006 to 2008, and the secondary clusters in two regions: northeastern China and western China. Besides, the secondary clusters of total TB notification rate had two more large clustering centers in Inner Mongolia, Gansu and Qinghai provinces and several smaller clusters in Shanxi, Henan, Hebei and Jiangsu provinces.


          The total TB notification cases clustered significantly in some special areas each year and the clusters trended to aggregate with time. The most-likely and secondary clusters that overlapped among two TB indicators had higher TB burden and risks of TB transmission. These were the focused geographic areas where TB control efforts should be prioritized.

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          Tuberculosis transmission by patients with smear-negative pulmonary tuberculosis in a large cohort in the Netherlands.

          Sputum smear microscopy is commonly used for diagnosing tuberculosis (TB). Although patients with sputum smear-negative TB are less infectious than patients with smear-positive TB, they also contribute to TB transmission. The objective of this study was to determine the proportion of TB transmission events caused by patients with smear-negative pulmonary TB in The Netherlands. All patients in The Netherlands with culture-confirmed TB during the period 1996-2004 were included in this study. Patients with identical DNA fingerprints in Mycobacterium tuberculosis isolates from sputum samples were clustered. The first patients in a cluster were considered to be the index patients; all other patients were considered to have secondary cases. In addition, we examined transmission from sources by conventional contact tracing. We analyzed 394 clusters with a total of 1285 patients. On the basis of molecular linkage only, 12.6% of the secondary cases were attributable to transmission from a patient with smear-negative TB. The relative transmission rate among patients with smear-negative TB, compared with patients with smear-positive TB, was 0.24 (95% confidence interval, 0.20-0.30). Secondary cases in clusters with an index patient with smear-negative TB more frequently had smear-negative status (odds ratio, 1.86; 95% confidence interval, 1.18-2.93), compared with secondary cases in clusters with an index patient with smear-positive TB. Conventional contact tracing revealed that 26 (6.2%) of the 417 sources, as identified by the Municipal Health Services, had smear-negative TB. In The Netherlands, patients with smear-negative, culture-positive TB are responsible for 13% of TB transmission. Countries that have ample resources should expand their TB-control efforts to include prevention of transmission from patients with smear-negative, culture-positive pulmonary TB.
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            Evaluation of investigations conducted to detect and prevent transmission of tuberculosis.

            Contact investigations are routinely conducted by health departments throughout the United States for all cases of active pulmonary tuberculosis (TB) to identify secondary cases of active TB and latent TB infection and to initiate therapy as needed in these contacts. Little is known about the actual procedures followed, or the results. To evaluate contact investigations conducted by US health departments and the outcomes of these investigations. Review of health department records for all contacts of 349 patients with culture-positive pulmonary TB aged 15 years or older reported from 5 study areas in the United States during 1996. Number of contacts identified, fully screened, and infected per TB patient; rates of TB infection and disease among contacts of TB patients; and type and completeness of data collected during contact investigations. A total of 3824 contacts were identified for 349 patients with active pulmonary TB. Of the TB patients, 45 (13%) had no contacts identified. Of the contacts, 55% completed screening, 27% had an initial but no postexposure tuberculin skin test, 12% were not screened, and 6% had a history of prior TB or prior positive tuberculin skin test. Of 2095 contacts who completed screening, 68% had negative skin test results, 24% had initial positive results with no prior test result available, 7% had documented skin test conversions, and 1% had active TB at the time of investigation. Close contacts younger than 15 years (76% screened vs 65% for older age groups; P<.001) or exposed to a TB patient with a positive smear (74% screened vs 59% for those with a negative smear; P<.001) were more likely to be fully screened. Close contacts exposed to TB patients with both a positive smear and a cavitary chest radiograph were more likely to have TB infection or disease (62% vs 33% for positive smear only vs 44% for cavitary radiograph only vs 37% for neither characteristic; P<.001). A number of factors associated with TB patient infectiousness, contact susceptibility to infection, contact risk of progression to active TB, and amount of contact exposure to the TB patient were not routinely recorded in health department records. Improvement is needed in the complex, multistep process of contact investigations to ensure that contacts of patients with active pulmonary TB are identified and appropriately screened.
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              The use of sighting data to analyse Iberian lynx habitat and distribution


                Author and article information

                Role: Editor
                PLoS One
                PLoS ONE
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                19 December 2013
                : 8
                : 12
                : e83605
                [1 ]National Center for Tuberculosis Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
                [2 ]School of Public Health, Fudan University, Shanghai, China
                [3 ]AIDS & Tuberculosis Unit, Ministry of Health and Child Welfare, Harare, Zimbabwe
                Arizona State University, United States of America
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: ZF WLX CSM HGX ZH XB. Performed the experiments: ZF. Analyzed the data: ZF. Contributed reagents/materials/analysis tools: ZF HF CJ HDM. Wrote the manuscript: ZF XB MT CJ HDM.


                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                : 17 June 2013
                : 5 November 2013
                This paper received supports from Chinese center for disease control and prevention funded by the Young Scholar Scientific Research Foundation of China CDC(2012A108) and TB Operational Research(TB12-007). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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