Population density, commercial air travel.
Social distancing is something that people even now are loathe to engage in, fortunately more and more people 'get it' but there are still plenty that do not. Arguably that's Darwin at work, but still.
Social distancing is something that people even now are loathe to engage in, fortunately more and more people 'get it' but there are still plenty that do not. Arguably that's Darwin at work, but still.