Heightened Vulnerability to MDR-TB Epidemics after Controlling Drug-Susceptible TB

Abstract

BackgroundPrior infection with one strain TB has been linked with diminished likelihood of re-infection by a new strain. This paper attempts to determine the role of declining prevalence of drug-susceptible TB in enabling future epidemics of MDR-TB.MethodsA computer simulation of MDR-TB epidemics was developed using an agent-based model platform programmed in NetLogo (See http://mdr.tbtools.org/). Eighty-one scenarios were created, varying levels of treatment quality, diagnostic accuracy, microbial fitness cost, and the degree of immunogenicity elicited by drug-susceptible TB. Outcome measures were the number of independent MDR-TB cases per trial and the proportion of trials resulting in MDR-TB epidemics for a 500 year period after drug therapy for TB is introduced.ResultsMDR-TB epidemics propagated more extensively after TB prevalence had fallen. At a case detection rate of 75%, improving therapeutic compliance from 50% to 75% can reduce the probability of an epidemic from 45% to 15%. Paradoxically, improving the case-detection rate from 50% to 75% when compliance with DOT is constant at 75% increases the probability of MDR-TB epidemics from 3% to 45%.ConclusionsThe ability of MDR-TB to spread depends on the prevalence of drug-susceptible TB. Immunologic protection conferred by exposure to drug-susceptible TB can be a crucial factor that prevents MDR-TB epidemics when TB treatment is poor. Any single population that successfully reduces its burden of drug-susceptible TB will have reduced herd immunity to externally or internally introduced strains of MDR-TB and can experience heightened vulnerability to an epidemic. Since countries with good TB control may be more vulnerable, their self interest dictates greater promotion of case detection and DOTS implementation in countries with poor control to control their risk of MDR-TB.

Two experiments for the price of one? The role of the second oscillation maximum in long baseline neutrino experiments

“…Since we found only very minor performance differences between the 60 GeV and 120 GeV options, we restrict the discussion to the 120 GeV beam in the following. Simulated spectra for all beam options have been kindly provided to us by the LBNE collaboration [40].…”

Some South African Rubiaceae Tree Leaf Extracts Have Antimycobacterial Activity Against Pathogenic and Non‐pathogenic Mycobacterium Species

“…It was responsible for the mortality of 1.4 million of the world's population in 2011, causing morbidity in an estimated 8.7 million cases (World Health Organization, 2011). Tuberculosis has become a global health problem with one-third of the world's population latently infected with the disease and one in ten people developing active disease in their lifetime (Bishai et al, 2010). Other than M. tuberculosis, other members of the M. tuberculosis complex such as Mycobacterium bovis, Mycobacterium africanum, Mycobacterium microti and Mycobacterium canetti have the ability to infect humans with TB (McGaw et al, 2008a).…”

A modeling of a Diphtheria epidemic in the refugees camps

“…Non-toxigenic strains produce a symptomatic, generally milder, disease ( [9], [12]). Four biotypes have been identied: gravis, mitis, intermedius and belfanti.…”