• Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Is smallpox contagious, and how long is it contagious?

Smallpox is highly contagious and remains contagious until all the scabs have fallen off. Usually, the contagious period takes about three to four weeks after the initial rash develops for the patient to be noncontagious.

What is the incubation period for smallpox?

The incubation period for smallpox is a little longer than that for many other viruses; symptoms develop about seven to 17 days after exposure.

How is smallpox transmitted?

Most transmission of smallpox is directly from person to person. Large, infectious droplets of saliva are expelled during coughing or sneezing and then inadvertently inhaled by another person. This usually requires close face-to-face contact and is similar to the way that mumps, measles, and influenza are spread. On average, a single individual would infect approximately 60% of their household contacts. Infected objects, such as used silverware or heavily contaminated bedding, may carry sufficient numbers of organisms to infect another person if improperly handled, although this route of transmission is much less common.

Medically Reviewed by a Doctor on 9/7/2016

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