Research activity
Geographic spread of measles
We investigated the spread of measles in the British Isles in conditions similar to the pre-vaccination era. Human mobility has a major influence over the main mechanisms underlying its dinamics. In particular, the relative importance of the different mechanisms changes according to the intensity of human mobility. We found that local periodicities and synchronization are influenced by human mobility, and that this influence leads to the occurrence of extended areas of stable in phase or opposition of phase synchronization. We also showed that persistence is related to disease circulation in highly populated areas and, because of this, survival of the diseases is possible even at low mobility levels.
Stochastic effects in the dynamics of infectious diseases
Whenever we study systems made up of many components, it is quite natural to talk about average values and their evolution. When the number of components of the system under study is small, these quantities are subjected to large fluctuations. In epidemiology, the standard models have focussed on the study of the average number of susceptibles and infectives to a disease. However, populations are composed of a finite number of individuals. This can result in huge stochastic fluctuations in the dynamics of infected individuals that, in some cases, can explain the multi-annual recurrence of certain diseases.
Stochastic fluctuations are amplified when spatial or temporal correlation are taken into account. We showed analytically how these fluctuations are enhanced in a standard model for infections spread (the SIR model) when the recovery from a disease is described realistically using gamma distributed recovery times: an important enhancement of the amplitude of fluctuations occurrs, and we can build an analytic expression in closed form at least for limiting cases.
Strain dynamics
How do influenza strains evolve and why do we have a pandemic every a few years? We have been investigating the possibility that an hetereogeneity in immune response in individuals based on their age could explain some of the facts observed for flu.
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Fig 1: In-phase (red) and opposition of phase (blue) with respect to London. Simulations performed with constant population size show the estabilishment of areas of stable phase synchronization with London. |
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Fig 2: How fluctiations change with the parameter controlling the gamma distribution. For L=1, recovery times are distributed exponentially, whilst for L -> oo, recovery becomes deterministic. For increasing L, fluctuations are amplified and their frequency increases. |
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Periodicity, synchronization and persistence in pre-vaccination measles
Ramona Marguta and Andrea Parisi
J. R. Soc. Interface, 13, 20160258 (2016) doi: 10.1098/rsif.2016.0258 [Abstract]Human mobility and the Dynamics of Measles in Large Geographical Areas
Ramona Marguta and Andrea Parisi
in "Proceedings of ECCS 2014", Springer Proceeding in Complexity. S. Battiston et al. (eds.), pp 169-179 (2016) doi: 10.1007/978-3-319-29228-1_15Power law jumps and power law waiting times, fractional calculus and human mobility in epidemiological systems
Nico Stollenwerk, Urszula Skwara, Lidia Aceto, Eric Daude, Ramona Marguta, Luís Mateus, Peyman Ghaffari, Andrea Parisi and Maíra Aguiar
in "Proceedings of the 14th Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2015",
ed. by J.V.-Aguiar, CMMSE (2015) pp. 1073-1268 [PDFormat]Impact of human mobility on the periodicities and mechanisms underlying measles dynamics
Ramona Marguta and Andrea Parisi
J. R. Soc. Interface, 12, 20141317 (2015) doi: 10.1098/rsif.2014.1317 [Article explained]Human mobility and measles
Ramona Marguta and Andrea Parisi
in "Proceedings of the 14th Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2014",
ed. by J.V.-Aguiar, CMMSE (2014) Vol. 3, pp. 868-870 [PDFormat]Stochastic amplification and childhood diseases in large geographical areas
Ramona Marguta and Andrea Parisi
in "Proceedings of the 13th Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2013",
ed. by I.P. Hamilton & J.V.-Aguiar, CMMSE (2013) Vol. 3, pp. 1001-1005 [PDFormat]Stochastic fluctuations in the susceptible-infective-recovered model with distributed infectious periods
A.J. Black, A.J. McKane, A. Nunes and A. Parisi
Physical Review E, 80(2), 021922 (2009)
also listed in Virtual Journal of Biological Physics Research 18(5), September-1 2009Heterogeneity in antibody range and the antigenic drift of influenza A viruses
A. Parisi, J.S. Lopes, A. Nunes, G. Gomes
Ecological Complexity, 14, 157 (2013). doi:10.1016/j.ecocom.2012.12.001Detecting and describing dynamic equilibria in adaptive networks
S. Wieland, A. Parisi, A. Nunes
European Physics Journal - Special Topics, 212(1), 99-113 (2012) [Preprint]Characterizing Steady-State Topologies of SIS Dynamics on Adaptive Networks
S. Wieland, T. Aquino, A. Parisi, A. Nunes
in "Proceedings of the European Conference on Complex Systems ECCS2010" [Preprint]