Because smallpox can only be transmitted from the time of the earliest appearance of rash, early detection of cases and prompt vaccination of all contacts is critical.
Also, an interesting piece of information from an aricle from Fox News:
The researchers cite the last case of naturally occurring smallpox in October 1977 as further evidence of the difficulty for one person to infect others. Of the 161 persons who had contact with the infected person, 12 unvaccinated persons had face-to-face contact. None of the 12 became ill with clinical cases of smallpox.
Unfortunately, there are some around here needlessly trying to scare people. Smallpox is a relatively easy disease to identify, and it is only contagious once the rash appears.
Not the case. Such a comment comes very close to being over the line.
See the reference cited, post 139 and address this:
Virus titers in saliva are highest the first week of infection, but infectivity can last up to 3 weeks (until the scabs fall off). Live virus can be cultured from scabs.
From Johns Hopkins:
The disease can spread from person to person. Transmission usually occurs only after the patient develops a fever and rash.
From the NYC Dept of Public Health:
Smallpox is transmitted by respiratory secretions, most efficiently during the early stages of the rash illness; it is generally believed that close person-to-person proximity is required for reliable transmission to occur. Patients are considered infectious from the time of development of the eruptive exanthem (usually 2-3 days after fever begins) until all scabs separate.