For group A streptococcus (GAS), an unknown fraction of infected hosts are asymptomatic carriers who may be able to spread disease whilst remaining symptom free. Such hosts tend to evade clinical attention making the true extent of asymptomatic carriage and the natural history of disease difficult to assess.
However, mathematical modelling studies of other infectious diseases have provided some insights into when we should expect carriers to play a significant role in transmission. But how universal are these insights? Are any of them likely to apply to GAS?
This presentation, will outline how we are addressing these questions. We undertook a literature review to determine the range of different approaches being used to incorporate carriers in models of infectious disease transmission. Four general modeling approaches were identified which, in their simplest formulations, are special cases of a unifying generic model of disease transmission with carriers. Our analysis of this unifying model provides a more complete understanding of the possible role of carriers in pathogen transmission, and has the potential to help guide model choice for future mathematical studies of GAS.
Our analysis underscores the importance of uncovering the fundamental nature of asymptomatic carriage for particular pathogens like GAS if future decisions on public health policy are to be based on the outputs of predictive mathematical models. An improved understanding of the role carriers play in the persistence of GAS infections will allow us to assess the likely impact of interventions, including vaccination, to reduce the burden of disease.