Thesis Defence: Incorporating Fear (Un)Learning Mechanisms in Infectious Disease Modelling

Avneet Kaur, supervised by Dr. Rebecca Tyson and Dr. Iain Moyles, will defend their thesis titled “Incorporating Fear (Un)Learning Mechanisms in Infectious Disease Modelling” in partial fulfillment of the requirements for the degree of Master of Science in Mathematics.

An abstract for Avneet Kaur’s thesis is included below.

Defences are open to all members of the campus community as well as the general public.

Registration is not required for in person defences.

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ABSTRACT

Effective management of epidemics requires not only modeling the disease itself but also the fear response of the population to both the disease and the vaccine. Risk perceptions of the disease may drive fear of disease in the population, thus encouraging people to adopt prophylaxis. On the other hand, negative thoughts about vaccines may drive fear of vaccines in the population, thus making some people vaccine hesitant. Since these fear responses affect population behaviour and thus disease transmission rate, fear responses in turn influence the disease trajectory.

In this thesis, we investigate an existing model of disease transmission that considers fear of disease and fear of vaccine as contagions that occur alongside the usual contagion of the disease. The mechanisms of fear acquisition and loss are rooted in human behavioural science. We analyse this model to determine the conditions under which each of the contagions (disease, fear of disease, or fear of vaccine) initially grows the fastest.

We then analytically investigate a reduced version of the full model with just the fear of disease (i.e., no vaccine or fear of vaccine). We consider this reduced model in two scenarios, one where fear is transmitted at a rate slower than that of the disease, and the other where the two transmission rates are comparable. In the former scenario, we show that behavioural change has little to no effect on the disease dynamics, but in the latter case, we observe that sufficient behavioural intervention can suppress the epidemic yielding bifurcations in final epidemic size, the number of infection waves, and their relative peak size. In both scenarios, we observe that the disease-fearful population may retain fear of disease even after the outbreak is over.

Finally, we propose an extension to the full model by adding a compartment for the population that is simultaneously fearful of both the disease and the vaccine. Analysis of the modified model gives us insights into the rich disease dynamics of this model. In particular, we observe that the final epidemic size remains low when a large fraction of the population either gets vaccinated or shifts to the double fear compartment.