In this seminar I aim to show you what happens to a theoretical physicist, who gets to work in Theoretical Immunology and Virology. During the journey the physicist gets to learn mathematics she did not know at the time, and of course, explores the biological universe at different scales.

Since we only have a limited amount of time, I would like to introduce you to a problem that I have recently become interested in, and which has received NIH funding. Co-infection of a single host by different pathogens is ubiquitous in nature. We consider a population of hosts (e.g., small or large vertebrates) and a population of ticks, both of them susceptible to  infection with two different strains of a given virus.  We note that for the purposes of our models, we have Crimean-Congo hemorrhagic fever virus (a segmented Bunyavirus) in mind, as the application system.

First, we focus on the dynamics of a single infection, proposing  a deterministic  model to understand the role of co-feeding in the transmission of the virus.  We then compute the basic reproduction number by making use of the next generation matrix approach.  When considering co-infection by two distinct strains (one resident and one invasive), we make use of differential equations to model the dynamics of susceptible, infected and co-infected species, and we compute the invasion reproduction number of the invasive strain.  I discuss some problems with the calculation, and the solution proposed by Samuel Alizon and Marc Lipsitch. I conclude with a perspective on how the co-infection model can be applied to HIV, and plans for future work and work in progress for tick-borne pathogens. To end the talk, I would like to showcase a number of problems in immunology I have worked on, and which have required, for instance, the theory of stochastic processes, probability generating functions, or the use of a Gröbner basis.