In one future, a monster wave hit in early 2020 (the current outbreak of millions of cases and a projected hundreds of thousands of deaths globally by August 1), but is followed by alternating mini-waves of much smaller outbreaks every few months with only a few (but never zero) cases in between.

In the second scenario, the current monster wave is followed later this year by one twice as fierce and even longer-lasting, as the outbreak rebounds after a summer when a significant drop in the number of cases and deaths led officials and individuals to let down their guard, relax physical distancing more than was safe, and fail to heed (or even detect) the early warning signs that a new outbreak was gathering force. After this doubly disastrous second wave, the sea is almost calm, marred only by an occasional wave of cases that number barely one-fifth of what the fall and spring of 2020 saw.

In the third possible future, the current wave creates a new normal, with Covid-19 outbreaks of nearly equal size and, in most cases, duration through the end of 2022. At that point, the best-case scenario is that an effective vaccine has arrived; if not, then the world experiences Covid-19 until at least half of the population has been infected, with or without becoming ill.