Foot-and-mouth disease (FMD) can affect a range of animals, including livestock. In South Africa, successful control has eliminated the infection from most of the country, however, infection risk remains in the areas surrounding the Kruger National Park. African buffalo (Syncerus caffer) maintain a high prevalence of FMD. Understanding how buffalo maintain the infection, when transmission from buffalo is most likely, and why transmission occurs are important to understanding FMD in South Africa. This article discusses an individual-based model that is guiding our field and experimental data collection in Kruger National Park.
Other infectious diseases
Individual-based models of sexually transmitted infection epidemics allow us to account for heterogeneity of sexual behaviour in a way that is impractical with traditional differential-equation-based models. But do we increase our knowledge by using more complex models? When we use sexual behaviour data in our models are we generating outputs, such as estimates of prevalence and mortality, that reflect the real-world populations we are studying? In this article we present examples that help us explore this question.
This article summarises two papers that have used individual-based models (IBMs) to assess intervention strategies for measles, which give a flavour of the types of scenarios and questions for which IBMs have been used. Together, these two papers highlight that IBMs can have varying levels of complexity, should, where possible, be fitted to data, must be subject to thorough sensitivity analyses in the case of missing data, and can be very useful for the assessment of intervention strategies in specific times and places.
Social mixing patterns can have an important effect on the spread of an infectious disease, and thus should be included in a model for the transmission of such a disease. Stride (a Simulator for the TRansmission of Infectious DisEases) is an open-source simulator for the transmission of infectious diseases. In Stride, the influence of age, context and type of day on social mixing patterns is explicitly modelled. After briefly introducing our model, we illustrate it by simulating the spread of Influenza in a synthetic population for Miami-Dade (Florida, USA).
Mathematical models are often used to gain theoretical insights into the epidemiology of sexually transmitted infections (STIs) and to inform policy around the prevention and treatment of STIs. Yet these models differ greatly in the assumptions they make, and can sometimes produce vastly different estimates of the likely impact of STI control programmes. So which modelling approaches are most realistic? How much bias might we be introducing with certain simplifying assumptions? This article summarises a recent paper that attempted to address these questions by comparing two broad modelling approaches: deterministic, frequency-dependent models and individual-based, network models.
Recent years have seen increasing recognition of the importance of canine rabies to human health: the scientific community has increasingly embraced dog rabies as an interesting and important field of study, and the public-health community has ramped up control efforts, leading to striking control successes, particularly in the Americas. This article discusses a series of papers published from 2007 based on ground-breaking work on tracing canine rabies in Tanzania, as well as analyses of data from other parts of the world.
Human cells have a finite lifespan (Hayflick limit). The existence of this Hayflick limit with regards to immune cells known as T cells, implies that infections have a long-term immunological cost (IC) to the individual because they drive immune cells towards the end of their lifespan, eventually making most of those cells unavailable to respond to other infections. The development of an accurate IC measure will lead to a better predictor of the age of the adaptive immune system than chronological age.
The biennial International AIDS Society (IAS) Conference on HIV Science was held in Paris, France in July 2017. This article presents some of the highlights of the conference, including the roll of PrEP and the promise of long-acting injectable ARVs, as well as contributions of SACEMA staff in the areas of HIV and Hepatitis C, and HIV and cervical cancer. Basic, clinical, epidemiological and operational research on HIV and the HIV response must continue to be prioritised even while we strengthen our health systems and improve the implementation of existing interventions.
An important goal of research in immunology is to understand the flaws in the human immune system, such that their impacts can be effectively mitigated. Previous work documented flaws in the mechanisms by which the immune system tempers its responses to pathogens in order to avoid harming the host. As explained here, these tempering mechanisms also govern the phenomenon of the original antigenic sin, whereby an encounter with a new pathogen strain preferentially recalls less potent immune responses directed against an older, moderately different strain.
As a PhD student in Ecology and Evolutionary Biology, I have spent more than half of the past four years of my dissertation work in Madagascar, where I study the transmission dynamics of zoonotic viruses which jump the species barrier from bat reservoirs to human hosts. I combine field, laboratory, and modeling methods, with each technique offering unique insights into the larger truth.