During epidemics of smallpox the anticipatory attitude of the physician's mind will often lead him to suspect as variola diseases which bear only a superficial resemblance to it. Contrariwise, in the absence of epidemic prevalence of smallpox, mild cases are apt to be overlooked. The latter error is much the more serious in its consequences, although the former may itself lead to embarrassing complications.
The detection of smallpox in its pustular stage, particularly in well-marked eruptions, is a facile matter even for the merest tyro in medicine. The picture of a profuse pustular variola can scarcely be mistaken for anything else. The diagnosis of the disease, however, in the first or second day of the eruption in mild cases, and especially in the absence of an epidemic, may present perplexities. Before the appearance of the eruption the diagnosis is difficult and often impossible. It may be surmised, but it is
SCHAMBERG JF. THE DIAGNOSIS OF SMALLPOX.. JAMA. 1902;XXXVIII(4):215-217. doi:10.1001/jama.1902.62480040001001