The global burden of tuberculosis (TB) has increased over the past two decades despite widespread implementation of control measures, suggesting that many of these strategies could be improved. Contact patterns of an index case and the susceptibility of the exposed individual are critical determinants of TB transmission. Contact patterns are significantly influenced by the existence of networks within a population. At the same time, HIV-infection has been the most important factor in the resurgence of TB worldwide by increasing the susceptibility of the exposed individual. However, no studies have carefully looked into the effect of transmission networks and HIV-infection in the dynamics of TB epidemics in the community. Most of the current infection control strategies are based on the concept that TB acquisition requires prolonged and close contact with an infectious case. However, recent TB outbreak investigations, affecting primarily HIV-infected patients, have failed to identify any link or evidence of close contact among cases infected with the same strain of M. tuberculosis, challenging this widely spread concept. Contrary to the establish paradigm, we believe that casual encounters, occurring within unrecognized transmission networks, are important drivers of TB epidemics in dynamic populations with high prevalence of HIV infection. Botswana offers unique opportunities to determine the role of HIV, the degree of contact to an index case and unrecognized social networks in TB epidemics. Over the last 6 years, we have developed a nationwide TB surveillance program in Botswana. We have seen that new TB cases without clear exposure to an index case are more frequently seen in the Southern areas of the country and are more frequently HIV- associated. Consistent with this observation, molecular genotyping of M. tuberculosis from sputum samples from HIV-infected patients from this area show that, despite the absence of known contact with an index case, most of them are infected with the same strain, suggesting recent infection from a common source. In contrast, TB in the Western region, which has one of the highest rates of TB in the world, is more HIV-independent, and close contact with an index case is often evident. Thus, we believe that there are distinct epidemics within the larger TB epidemic in Botswana that are fueled by different mechanisms of transmission and acquisition, probably related to the population dynamics (close vs. casual exposures) and prevalence of HIV infection. In this proposal, we aim to determine the relative role of these factors (HIV, the degree of contact to an index case and unrecognized social networks) as drivers of the TB epidemics in these 2 populations by combining classical epidemiologic methods and molecular epidemiology. We expect this study will show that casual encounters, primarily occurring in unrecognized transmission networks, are the main drivers of TB epidemics in populations with high prevalence of HIV, which would represent a change in current paradigms.

Public Health Relevance

The demonstration that casual encounters, occurring primarily in nosocomial settings, are in fact the main drivers of TB epidemics in populations with high prevalence of HIV, will represent a major change in current paradigms leading to changes in public health and infection control interventions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
1R01AI097045-01
Application #
8210750
Study Section
AIDS Clinical Studies and Epidemiology Study Section (ACE)
Program Officer
Huebner, Robin E
Project Start
2011-09-01
Project End
2016-08-31
Budget Start
2011-09-01
Budget End
2012-08-31
Support Year
1
Fiscal Year
2011
Total Cost
$629,230
Indirect Cost
Name
University of Pennsylvania
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Shin, S S; Modongo, C; Zetola, N M et al. (2018) High rates of exposure to tuberculosis patients among HIV-infected health care workers in Botswana. Int J Tuberc Lung Dis 22:366-370
Shin, Sanghyuk S; Modongo, Chawangwa; Baik, Yeonsoo et al. (2018) Mixed Mycobacterium tuberculosis-Strain Infections Are Associated With Poor Treatment Outcomes Among Patients With Newly Diagnosed Tuberculosis, Independent of Pretreatment Heteroresistance. J Infect Dis 218:1974-1982
Surie, Diya; Fane, Othusitse; Finlay, Alyssa et al. (2017) Molecular, Spatial, and Field Epidemiology Suggesting TB Transmission in Community, Not Hospital, Gaborone, Botswana. Emerg Infect Dis 23:487-490
Gu, Diane; Modongo, Chawangwa; Shin, Sanghyuk S et al. (2017) Geospatial modelling in guiding health program strategies in resource-limited settings-the way forward. Ann Transl Med 5:499
Shin, Sanghyuk S; Modongo, Chawangwa; Boyd, Rosanna et al. (2017) High Treatment Success Rates Among HIV-Infected Multidrug-Resistant Tuberculosis Patients After Expansion of Antiretroviral Therapy in Botswana, 2006-2013. J Acquir Immune Defic Syndr 74:65-71
Zetola, Nicola M; Modongo, Chawangwa; Matsiri, Ogopotse et al. (2017) Diagnosis of pulmonary tuberculosis and assessment of treatment response through analyses of volatile compound patterns in exhaled breath samples. J Infect 74:367-376
Zetola, Nicola M; Grover, Surbhi; Modongo, Chawangwa et al. (2016) Collision of Three Pandemics: The Coexistence of Cervical Cancer, HIV Infection, and Prior Tuberculosis in the Sub-Saharan Country of Botswana. J Glob Oncol 2:47-50
Zetola, N M; Modongo, C; Moonan, P K et al. (2016) Protocol for a population-based molecular epidemiology study of tuberculosis transmission in a high HIV-burden setting: the Botswana Kopanyo study. BMJ Open 6:e010046
Shin, Sanghyuk S; Modongo, Chawangwa; Zetola, Nicola M (2016) The impact of mixed infections on the interpretation of molecular epidemiology studies of tuberculosis. Int J Tuberc Lung Dis 20:423-4
Bisson, Gregory P; Zetola, Nicola; Collman, Ronald G (2015) Persistent high mortality in advanced HIV/TB despite appropriate antiretroviral and antitubercular therapy: an emerging challenge. Curr HIV/AIDS Rep 12:107-16

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