The question of why the virus has overwhelmed some places and left others relatively untouched is a puzzle that has spawned numerous theories and speculations but no definitive answers. That knowledge could have profound implications for how countries respond to the virus, for determining who is at risk and for knowing when it’s safe to go out again.

There are already hundreds of studies underway around the world looking into how demographics, pre-existing conditions and genetics might affect the wide variation in impact.

Roll of the Dice

Finally, most experts agree that there may be no single reason for some countries to be hit and others missed. The answer is likely to be some combination of the above factors, as well as one other mentioned by researchers: sheer luck.

Countries with the same culture and climate could have vastly different outcomes if one infected person attends a crowded social occasion, turning it into what researchers call a super-spreader event.