Infectious disease dynamics: individuals, populations and ecosystems
Monday 22 October 2012
Prof.dr. Hans Heesterbeek
Department of Farm Animal Health, UU
The dynamics of infectious disease agents in populations of hosts depend on characteristics of agent, a diverse range of traits of the host, the interaction between agent and host, the network of relations between hosts, and characteristics of the environment in which all these encounters take place. These interactions produce, as a rule, a complex system of positive and negative feedback spanning different levels of biological integration. The main interest of my research is in understanding this complexity and how these heterogeneities and interactions shape the observed dynamics.
An example that is studied in great detail in an international collaboration concerns plague (Yersinia pestis) in Kazakhstan, where the main host is the great gerbil. The population dynamics of this rodent and its fleas is heavily influenced by climate and the environment, and the ecology of interaction between rodents can be used to explain plague outbreaks in a data set of more than 50 years, as well as explain the dynamics in human cases. The study combines expertise in field ecology, epidemiology, remote sensing, geology, mathematics and phylodynamics.
An important aspect we study there and across infectious disease dynamical systems concerns thresholds for changing intrinsic and extrinsic factors that, when crossed, force the system into different macroscopic behaviour (for example, emergence, epidemics, local fade out or elimination, periodic outbreaks). A theoretical framework we developed is widely used to characterise and understand such thresholds.
Most systems we study concern infectious agents in wild animal populations and in human populations, and notably on the interface between the two. In the coming years a focal point of the research will be the role and dynamics of infectious agents in communities of host species, such as food webs and ecosystems. The increase in the emergence of infectious agents coming from wildlife to humans in the last 40 years is partly related to shifts in macroscopic behaviour of ecosystems where host and non-host species of such an agent interact and where thresholds in this interaction can shift the balance of stability leading to changes in prevalence. We will both develop theoretical methods which allow the study of these systems, but also be guided by close scrutiny of real systems, notably contrasting plague dynamics in different regions of the world and contrasting dynamics of a range of infections in tri-trophic food webs of the savannah ecosystems of the Serengeti, Kruger and Etosha National Parks
Diekmann, O., Heesterbeek, J.A.P. & T. Britton: Mathematical Tools for Understanding Infectious Disease Dynamics. Princeton University Press, 540pp, 2012
Reijniers, J., Davis, S., Begon, M., Heesterbeek, J.A.P., Agayev, V.S. & H. Leirs (2012): A curve of thresholds governs plague epizootics in Central Asia. Ecol. Letters, 15, 554-560.
Severins, M., Klinkenberg, D. & J.A.P. Heesterbeek (2012). How selective forces dictate the variant surface antigens used by malaria parasites. J. R. Soc. Interface, 9, 246-260.
Noelle Samia , Kyrre Kausrud , Hans Heesterbeek , Vladimir Ageyev , Mike Begon, Kung-Sik Chan , Nils Chr. Stenseth (2011). The dynamics of the plague-wildlife-human system in Central Asia is controlled by two epidemiological thresholds. PNAS, 108, 14527-14532.
Diekmann, O., Heesterbeek, J.A.P. & M.G. Roberts (2010). On the Construction of next-generation matrices for compartmental epidemic models. J. R. Soc Interface, 7, 873-885.
Davis, S.A., Trapman, J.P., Leirs, H., Begon, M. & J.A.P. Heesterbeek (2008). The abundance threshold for plague as a critical percolation phenomenon. Nature, 454, 634-637.
Neutel, A.M., Heesterbeek, J.A.P., van de Koppel, J., Hoenderboom, G., Vos, A., Kaldeway, C., Berendse, F. & P.C. de Ruiter (2007). Reconciling complexity with stability in naturally assembling food webs. Nature, 449, 599-602.
Neutel, A.M., Heesterbeek, J.A.P. & P.C. De Ruiter (2002): Weak links in long loops enhance stability in real food webs. Science, 296, 1120-1123.