A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS

Abstract

VOLUME 33 NÚMERO 4 AGOSTO 1999© Copyright Faculdade de Saúde Pública da USP. Proibida a reprodução mesmo que parcial sem a devida autorização do Editor Científico. Proibida a utilização de matérias para fins comerciais. All rights reserved. The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. Methods Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. Revista de Saúde Pública ResultsThe results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. ConclusionIt is concluded that in the case of a host population with a low (high) rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more) virulent strain prevails. Descritores

Transient virulence of emerging pathogens

“…Observing virulence dynamics in the wild is far more difficult. There has been a decade and a half of debate over the expected trajectory of virulence evolution in HIV (Ewald 1991;Bonhoeffer & Nowak 1994;Lipsitch & Nowak 1995;Massad 1996;Lipsitch 1997;Coutinho et al 1999;Levin et al 2001;Courgnaud et al 2004). While recent studies suggest that subtypes with lower fitness now dominate, the empirical evidence on the trajectory of virulence is still somewhat ambiguous (Ariën et al 2005(Ariën et al , 2007Mü ller et al 2006Mü ller et al , 2009Herbeck et al 2008)-perhaps not surprising given the complexity of HIV, which has multiple subtypes, inhabiting many genotypes of hosts, multiple tissue types, and with hugely variable ecological and evolutionary pressures at different stages of infection of a single host.…”

Fuzzy gradual rules in epidemiology

“…The simplest case of the dynamics of infectious disease is the so-called susceptible-infected-susceptible (SIS) model (Coutinho et al, 1999;Lopez et al, 1999;Massad et al, 1995;Struschiner et al, 1999). In this model, susceptible individuals can become infected if they have one infective contact with any infected individual.…”

“…This may cause a tremendous amount of imprecision and uncertainty in the interpretation of effect measures in analysis. Furthermore, in general, mathematical functions that are able to describe the epidemiological variables correlation are not available (Coutinho et al, 1999;Lopez et al, 1999;Massad et al, 1995Massad et al, , 2001. Our own experience in dealing with epidemiology and fuzzy epidemic modelling have demonstrated that in the case of biological, and particularly epidemiological models, it is often hard to find functional information about the dynamics of the systems.…”

A schematic age-structured compartment model of the impact of antiretroviral therapy on HIV incidence and prevalence

“…This relative contribution may have important consequences to the epidemiological pattern of HIV transmission, as well as to the assessment of the impact of HIV treatment on the epidemiology of HIV/AIDS. In addition, it should be expected that differences in the probability of transmission in each of the distinct phases of the infection may also have important consequences on the evolution of HIV virulence [4].…”