Implications of psoriasis as a new disease

It is noted that psoriasis appears not to have been described until the return of explorers from the New World back to the Old. Thus, it is suggested that in fact psoriasis is a new disease to the Old World. One implication of this is that any infectious agent which is a candidate cofactor in the pathogenesis of psoriasis must itself be new to the Old World after the time of the explorers.