The frequency of pandemics is not linear in time, but it is a function of people density, overpopulation and hygienic habits and similar (like politicisation of health).
Number of people did grow over the last hundred years following an exponential curve. Stupidity grew exponentially as well (only braindead idiots like anti vaxers and ultra rights politicise health). Make of that what you want, but I would expect the next pandemics knocks earlier on our doors ....