Ecological interference between fatal diseases

Abstract

An important issue in population biology is the dynamic interaction between pathogens. Interest has focused mainly on the indirect interaction of pathogen strains, mediated by cross immunity. However, a mechanism has recently been proposed for 'ecological interference' between pathogens through the removal of individuals from the susceptible pool after an acute infection. To explore this possibility, we have analysed and modelled historical measles and whooping cough records. Here we show that ecological interference is particularly strong when fatal infections permanently remove susceptibles. Disease interference has substantial dynamical consequences, making multi-annual outbreaks of different infections characteristically out of phase. So, when disease prevalence is high and is associated with significant mortality, it might be impossible to understand epidemic patterns by studying pathogens in isolation. This new ecological null model has important consequences for understanding the multi-strain dynamics of pathogens such as dengue and echoviruses.

Dynamic effects of antibody-dependent enhancement on the fitness of viruses

“…We believe this assumption is a reasonable because of the low case fatality rate of DHF (Ϸ0.01) and the much lower fatality rate of dengue infection (Ϸ0.0001) in Thailand (34). The work of Kawaguchi and Rohani (30,35) suggests that the dynamics of dengue are significantly impacted by dengue-induced mortality only at much higher levels of mortality than are observed. The rate of recovery, given by , is assumed to be equal for primary and secondary infections.…”

Independent and Competing Disease Risks: Implications for Host Populations in Variable Environments

“…Seasonal pathogens might therefore function as competing disease risks among each other while remaining independent of many other risk factors. Competitive interactions among seasonal pathogens can have substantial disease dynamic consequences (Rohani et al 1998(Rohani et al , 2003. We hypothesize that they may also modify disease impacts on the host population.…”

Cross-immunity between strains explains the dynamical pattern of paramyxoviruses

“…Cross-immunity acts by reducing the rate at which a host that has recently recovered from one pathogen may become infected with another (38). Convalescence acts by temporarily removing individuals after infection because of behavioral modification and thus, transiently reducing the susceptible pools of the infections (43). Our models include seasonally forced transmission dynamics and temporary immunity of acquired infection.…”

“…Using statistical likelihoods, we compare two hypothetical mechanisms of interaction between diseases: cross-immunity (immune-mediated interaction) (37)(38)(39)(40)(41)(42) and convalescence (ecological interaction) (43,44). Accurate assessment of the nature of interaction among these viruses has important potential public health consequences for prediction of outbreaks and control of disease by targeting and timing of control strategies.…”