COMPLEXDYNAMICS-PHIM · On the Origin of Complex Dynamics in Multi-strain Models: Insights for Public Health Intervention Measures

On the Origin of Complex Dynamics in Multi-strain Models: Insights for Public Health Intervention Measures

The dynamics of infectious diseases are by nature non-linear and the understanding of such non-linear processes is vital, both for medical and economic reasons. The problem is mathematically difficult and to make the urgently needed progress in our understanding of such dynamics, concepts from various fields of mathematics as well the availability of good data for model evaluation are needed. Dengue fever (DF) is one example of a viral mosquito-borne infection, a major international public health concern. With 2.5 billion people at risk of acquiring the infection, it is estimated that around 400 million dengue infections occur every year, of which 96 million manifest symptoms with any level of disease severity. DF is caused by four antigenically related but distinct serotypes (DENV-1 to DENV-4). Infection by one serotype confers life-long immunity to that serotype and a period of temporary cross-immunity to other serotypes. The clinical response on exposure to a second serotype is complex and there is good evidence that sequential infection increases the risk of developing severe disease, due to a process described as antibody-dependent enhancement (ADE), where the pre-existing antibodies to previous dengue infection do not neutralize but rather enhance the new infection. DF epidemiological dynamics shows large fluctuations in disease incidence, and several mathematical models describing the transmission of dengue viruses have been proposed to explain the irregular behavior of dengue epidemics. Multi-strain dengue dynamics have been modeled with extended SIR-type models including immunological aspects of the disease such as ADE phenomenology. A minimalistic two-infection dengue model (with at least two different serotypes to describe differences between primary and secondary infections), developed by Maíra Aguiar and collaborators (JTB, 2011) has found deterministic chaos in much wider parameter regions (not predicted by previous models), indicating that deterministic chaos is much more important in multi-strain models than previously thought and opening new ways to the analysis of existing data sets. The mechanisms described for dengue, where complex dynamics were observed to happen in a very simple models, are likely to be present in other diseases caused by multiple strains where large fluctuations have been observed and up to now not well understood. Led by Marie Sklodowska-Curie Research Fellow Maíra Aguiar, the EU-funded COMPLEXDYNAMICS-PHIM project has developed simple mathematical models able to address specific public health questions. The main objective of this project was to study the origin of the chaotic dynamics in multi-strain epidemiological models, identifying the mechanisms needed to generate the complex behavior found in the well studied minimalistic dengue models (Aguiar et al, JTB, 2011).

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз