Smallpox incubation period/smallpox contagion

Federal Smallpox Plan Promises Aggressive Response if Contagious Virus Is Released

To breathe in the virus and catch smallpox, a person must be within about six feet of a patient suffering the characteristic rash. Those who live or work near a patient are vaccinated just as a precaution.

Smallpox symptoms include fever and a pock-like rash all over the body, appearing between seven and 17 days after exposure to the virus. People are contagious from the time the rash appears - particularly in the first week of illness - until the scabs fall off.

Old Smallpox Vaccines May Still Help

There is a window of up to 11 days between the time people contract the virus and the time they actually become sick and develop the scabs that make the disease contagious.

Particularly in a time of heightened alert, doctors say they would probably be able to recognize a small outbreak during that window and quickly vaccinate people who came in contact with the victims.

``It has a rather slow evolution,'' LeDuc said. "We think it's not going to be a wildfire."

CDC's Response Plan for a Smallpox Emergency Excludes Mass Vaccination

Dr. Henderson wants to allay public fears regarding the potential consequences of a bioterrorism attack with the variola virus. "People are afraid that someone who is infected could spread the infection widely by traveling on an airplane."

That's not realistic, he pointed out, because there is an incubation period of 10 to 12 days, followed by 2 to 3 days of high fever and prostration with severe headache and backache. "It's only after that point, when the rash begins, that the individual can transmit the disease. However, people are likely to feel quite poorly and to be staying in bed, not traveling around the country."

Smallpox Contingency Plan Revealed

It takes fairly close proximity, within about six feet of a person suffering the characteristic rash, to breathe in the smallpox virus and catch the disease. Quickly vaccinating those who live with or work around a patient is protective. 

World Health Body Rules Out Mass Smallpox Jabs

Another argument against mass inoculation is that the smallpox vaccine can be administered after the disease has been contracted, provided it is detected quickly, WHO head of communicable diseases David Heymann said.

The incubation period for smallpox is seven to 14 days and the vaccine is effective if given within four days of infection.

Vaccinia (Smallpox) Vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2001

Symptoms of smallpox begin 12--14 days (range: 7--17) after exposure, starting with a 2--3 day prodrome of high fever, malaise, and prostration with severe headache and backache. This preeruptive stage is followed by the appearance of a maculopapular rash (i.e., eruptive stage) that progresses to papules 1--2 days after the rash appears; vesicles appear on the fourth or fifth day; pustules appear by the seventh day; and scab lesions appear on the fourteenth day (Figures 1,2) (3). The rash appears first on the oral mucosa, face, and forearms, then spreads to the trunk and legs (3,4). Lesions might erupt on the palms and soles as well. Smallpox skin lesions are deeply embedded in the dermis and feel like firm round objects embedded in the skin. As the skin lesions heal, the scabs separate and pitted scarring gradually develops (Figure 2) (4). Smallpox patients are most infectious during the first week of the rash when the oral mucosa lesions ulcerate and release substantial amounts of virus into the saliva. A patient is no longer infectious after all scabs have separated (i.e., 3--4 weeks after the onset of the rash).