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Implications of partial immunity on the prospects for tuberculosis control by p...
Gomes, M. G. M.; Rodrigues, P.; Hilker, F. M.; Mantilla-Beniers, N. B.; Muehlen, M.; Paulo, A. C.; Medley, G. F.One-third of the world population (approximately 2 billion individuals) is currently infected with Mycobacterium tuberculosis, the vast majority harboring a latent infection. As the risk of reactivation is around 10% in a lifetime, it follows that 200 million of these will eventually develop active pulmonary disease. Only therapeutic or post-exposure interventions can tame this vast reservoir of infection. Trea...
Dynamical behaviour of epidemiological models with sub-optimal immunity and non...
Gomes, M. G. M.; Margheri, A.; Medley, G. F.; Rebelo, C.In this paper we analyze the dynamics of two families of epidemiological models which correspond to transitions from the SIR (susceptible-infectious-resistant) to the SIS (susceptible-infectious-susceptible) frameworks. In these models we assume that the force of infection is a nonlinear function of density of infectious individuals, I. Conditions for the existence of backwards bifurcations, oscillations and Bo...
The reinfection threshold
Gomes, M. G. M.; White, L. J.; Medley, G. F.Thresholds in transmission are responsible for critical changes in infectious disease epidemiology. The epidemic threshold indicates whether infection invades a totally susceptible population. The reinfection threshold indicates whether self-sustained transmission occurs in a population that has developed a degree of partial immunity to the pathogen (by previous infection or vaccination). In models that combine...
Infection, reinfection, and vaccination under suboptimal immune protection: epi...
Gomes, M. G. M.; White, L. J.; Medley, G. F.The SIR (susceptible-infectious-resistant) and SIS (susceptible-infectious-susceptible) frameworks for infectious disease have been extensively studied and successfully applied. They implicitly assume the upper and lower limits of the range of possibilities for host immune response. However, the majority of infections do not fall into either of these extreme categories. We combine two general avenues that strad...
The reinfection threshold promotes variability in tuberculosis epidemiology and...
Gomes, M. G. M.; Franco, A. O.; Gomes, M. C.; Medley, G. F.Population patterns of infection are determined largely by susceptibility to infection. Infection and vaccination induce an immune response that, typically, reduces susceptibility to subsequent infections. With a general epidemic model, we detect a 'reinfection threshold', above which reinfection is the principal type of transmission and, consequently, infection levels are much higher and vaccination fails. The...
On the determinants of population structure in antigenically diverse pathogens
Gomes, M. G. M.; Medley, G. F.; Nokes, D. J.Many pathogens exhibit antigenic diversity and elicit strain-specific immune responses. This potential for cross-immunity structure in the host resource motivates the development of mathematical models, stressing competition for susceptible hosts in driving pathogen population dynamics and genetics. Here we establish that certain model formulations exhibit characteristics of prototype pattern-forming systems, w...
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