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The world’s last case of
smallpox, which was due to infection with variola major virus, occurred
in 1978. This disease is ancient and played many roles in the course
of history. For example, many members of various royal families,
including Louis XV of France, died of this illness. The global elimination
of smallpox by vaccination remains a major historical and medical
milestone. Routine vaccination against smallpox was discontinued
in the United States in 1972.1-4 There was a brief
resurrection of use of vaccine in the United States during the early
2000s when there was fear that the virus might be used as an agent
of bioterrorism.5,6 The smallpox vaccine contains live
vaccinia virus, which confers protection against infection from variola
virus, the cause of smallpox. Vaccinia virus can be transmitted
from a vaccine recipient to other persons through direct (skin-to-skin)
contact via material from the unhealed vaccination site or through
indirect contact by means of fomites. This can result in eczema
vaccinatum, a life-threatening complication of vaccinia virus infection
(eFig. 322.1) no longer seen since use of
the vaccine was discontinued. This brief chapter is included in
this textbook to mark the momentous medical event of disease elimination
and to remind medical personnel of the disease that once existed and,
it is hoped, will remain forever gone.
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Smallpox is caused by variola virus, a member of the Poxvirus
family. It is one of the largest and most complex DNA viruses. For
this reason it is easily identified by electron microscopy. This
virus is, however, highly contagious and quite stable. It is not
a virus to be easily reckoned with. Related viruses include monkeypox,
vaccinia, and cowpox.3,4
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Smallpox begins with symptoms such as high fever, malaise, pain
(typically in the back, abdomen, and head), and prostration. About
24 hours before onset of rash, an enanthem occurs on the oral mucosa.
The rash begins on the face and is centrifugal in distribution (in
contrast to varicella, with which it used to be confused). Rash
is often present on the palms and soles. Rash progresses from macules
to papules and pustules, some of which may become umbilicated. Rash lesions
are all in the same stage of development, in contrast to varicella
in which macules, papules, and pustules coexist in one area of skin.
Smallpox is highly contagious while the rash is evolving, and its
evolution may take several weeks. Untreated, unvaccinated patients
who develop smallpox have a fatality rates as high as 30%, with
highest mortality rates in infants and adults.3
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Diagnosis can be made rapidly by viewing vesicular lesions with
electron microscopy. Patients in whom the diagnosis of smallpox
is seriously being ...