Tradeoff between speed and infectivity in pathogen evolution

ABSTRACT

Given the present pandemic and the constantly arising new variants of SARS-CoV-2, there is an urgent need to understand the factors driving disease evolution. Here, we investigate the tradeoff between the speed at which a disease progresses and its reproductive number. Using SEIR and agent-based models, we show that in the exponential growth phase of an epidemic, there will be an optimal duration of new disease variants, balancing the advantage of developing fast with the advantage of infecting many new people. In the endemic state this optimum disappears, and lasting longer is always advantageous for the disease. However, if we take into account the possibility of quarantining the infected, this leads to a new optimum disease duration emerging. This work thereby comments on the observation of ever shorter generation times in the evolution of variants of SARS-CoV-2 from the original strain to the Alpha, Delta, and finally Omicron variants.