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As far as the disease itself, the most important thing to remember is that it is NOT contagious in its initial stages. Only after the appearance of the telltale rash, usually after 10 or 12 days, does the disease become contagious.

You sure about that?

I've read that smallpox is contagious during incubation, prior to the manifestation of symptoms. There were also several smallpox threads on the subject last week, with comments from doctors, and none suggested that the virus wasn't contagious prior to the development of pustules.

You sure about that?

I'm positive.

From this article in JAMA, which, BTW, took all of 30 seconds to find using Google:

Historically, the rapidity of smallpox transmission throughout the population was generally slower than for such diseases as measles or chickenpox. Patients spread smallpox primarily to household members and friends; large outbreaks in schools, for example, were uncommon. This finding was accounted for in part by the fact that transmission of smallpox virus did not occur until onset of rash. By then, many patients had been confined to bed because of the high fever and malaise of the prodromal illness. Secondary cases were thus usually restricted to those who came into contact with patients, usually in the household or hospital.

There is a lot of scare mongering going on around here lately. Anything you read (including this) should be taken with a grain of salt. Although information like this is very easy to confirm.

According to the APHA's manual of infectious disease, "CONTROL OF COMMUNICABLE DEISEASES IN MAN" (1990) the incubation period is from 7 to 17 days, and the period of communicability starts with the appearance of the first skin lesions, lasting until ALL lesions (and scabs) have disappeared- up to 3 weeks in many cases.

I've read that smallpox is contagious during incubation, prior to the manifestation of symptoms. There were also several smallpox threads on the subject last week, with comments from doctors, and none suggested that the virus wasn't contagious prior to the development of pustules.

I'm not an expert, but based on what very little I know, I would guess that there is probably at least a very narrow window of opportunity between the moment when the earliest symptoms develop and the earliest moment when the symptoms would be obvious enough to make smallpox a suspicion. In other words, during those first few hours when you start coming down with something, you usually don't know for sure whether it is just a cold, the flu, or something more serious. It is that time period when a contagious kid could infect dozens at school, maybe more dozens on the school bus, the rest of the family, then dozens more in the waiting room. All within the course of perhaps three or four hours.