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Introduction:
Smallpox is a disease caused by a poxvirus that is transmitted from person to person that causes
high fever, characteristic rash, and may kill about one-third of those infected. Smallpox also
called variola.
Due to the success of an intense worldwide public health initiative, not one documented
naturally occurring case of this highly infectious, deadly disease has occurred since Oct. 26,
1977. (An unvaccinated hospital cook in Somalia was the last person to naturally contract
smallpox.) The World Health Organization (WHO) officially declared smallpox eradicated in
1980.
History of smallpox:
For centuries, smallpox affected political and social agendas. Evidence of smallpox infection has
been found in Egyptian mummies. Smallpox epidemics plagued Europe and Asia until 1796,
when Edward Jenner tested his theory of disease protection. He did this by inoculating a young
boy with material obtained from a milkmaid who was infected with the milder cowpox virus. The
success of that experiment led to the development of a vaccine (from vacca, the Latin word for
cow). Afterward, the incidence of smallpox infection in Europe steadily declined.
In the Americas, smallpox severely weakened the native population. They had never been
exposed to smallpox, which the European explorers brought with them to the Americas in the
1600s. The British forces at Fort Pitt purposefully gave smallpox-contaminated blankets and
goods to Native Americans during the French and Indian Wars in an attempt to weaken the
Native American resistance to colonial expansion. Due to this and through natural spread, the
epidemic that followed killed half of the Native American population.
Once the disease and its method of spread were understood more thoroughly, smallpox
vaccination became mandatory in developed countries in the early 1900s. The development of
the vaccinia virus, coupled with aggressive immunization, led to the eventual control and
eradication of smallpox in 1977.
Since the last documented "naturally occurring" case in 1977, only two deaths from smallpox
have been reported (1978 in Birmingham, England). Both deaths were the result of laboratory
accidents.
Current locations of Smallpox Virus:
Only two laboratories in the world are known to house smallpox virus: the Centers for Disease
Control and Prevention (CDC) in Atlanta, Ga., and the State Research Center of Virology and
Biotechnology in Koltsovo, Russia.
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Dr. Ken Alibek, a former senior microbiologist in the Russian Offensive Biological Weapons
Program, has alleged that, in 1980, the Soviet Union started large-scale production of the
smallpox virus and genetic recombination of more potent strains. Since the fall of the Soviet
Union, concern exists that this knowledge may be used in other countries. The extent of smallpox
stockpiles in other countries is unknown but may have become substantial since the collapse of
the Soviet Union.
The consequences of a smallpox outbreak can only be estimated. About 30% of unprotected
people who are exposed to a person with smallpox would themselves become infected. Of these,
30% would probably die from infection. Diagnosis is difficult during early stages of the disease.
Presently, insufficient supplies of vaccine exist to ensure eradication of smallpox in case the
disease is released intentionally in a large-scale attack.
Smallpox Causes:
Variola (the virus that causes smallpox) is a member of the orthopoxvirus genus, which also
includes viruses that cause cowpox, monkeypox, or, and molluscum contagiosum. Poxviruses are
the largest animal viruses, visible with a light microscope. They are larger than some bacteria
and contain double-stranded DNA.
Poxviruses are the only viruses that do not need a cell's nucleus to replicate inside the cell. The
variola virus is the only known cause of smallpox. The disease affects only humans. No animal
reservoirs or insect vectors (insects that spread a disease) exist, and no carrier state (period when
the virus is in the body, but the person is not actively sick) occurs.
Before smallpox was wiped out, the disease survived through continual person-to-person
transmission. Pregnant women and children had a heightened risk for the illness. Smallpox also
affected them more severely than normal. The virus is only transmitted from human to human;
there are no known animal infections. The virus is acquired from inhalation (breathing into the
lungs). Virus particles can remain on such items as clothing, bedding, and surfaces for up to one
week.
The virus starts in the lungs. From there, the virus invades the bloodstream and spreads to the
skin, intestines, lungs, kidneys, and brain. The virus activity in the skin cells creates a rash that
starts as macules (flat, red lesions). After this, vesicles (raised blisters) form. Then, pustules
(pus-filled pimples) appear about 12-17 days after a person becomes infected. Survivors of
smallpox often have severely deformed skin from the pustules.
Types:
Variola major, or smallpox, has a death rate of 30%. Variola minor, or alastrim, is a milder form
of the virus with a death rate of 1%. Four types of variola exist: classic, hemorrhagic, malignant,
and modified.
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Classic smallpox is believed to be the most communicable disease; about 30% of unvaccinated
people who come in contact with it become infected.
The hemorrhagic variety of variola has a much higher death rate (95%) than classic smallpox and
leads to death more quickly. Infected people often die before the pustules form. This variety is
recognizable by certain types of bleeding sores in mucous tissues. Comprehensive studies
documenting almost 7,000 cases of variola found 200 people had this form of the disease (192
died). Pregnant women are more likely to contract this version.
Prior to eradication, the malignant or flat form of smallpox affected 6% of the population and
evolved more slowly than the classic type. Lesions were flat, often described as feeling velvety.
The death rate for this form approaches 100%.
The modified variety of smallpox essentially affects people who have been vaccinated and still
have some immune response to the vaccine. In a vaccinated population, this version could affect
about 15%.
Smallpox Signs and Symptoms`:
After infection, symptoms may take from seven to 17 days to appear for major types of smallpox
People who have contracted smallpox initially develop such symptoms as fever, body
aches, headache, chills, and, particularly, backache.
When the rash appears, the virus is highly contagious as it moves into the mucous membranes.
The body sheds the cells, and virus particles are released, coughed, or sneezed into the
environment. The infected person can be infectious for up to three weeks (until the scabs fall off
the rash). Live virus can be present in the scabs. After the scabs or crusts fall off (in two to four
weeks), a depression or light-skinned scar remains.
Early in the course of the disease, the rash and pus-filled sores can easily be mistaken
for chickenpox. Lesions occur first in the mouth and spread to the face, then to the forearms and
hands, and finally to the lower limbs and trunk. In contrast, rash from chickenpox progresses from
the arms and legs to the trunk and rarely forms in the armpits, palms, soles, and elbow areas.
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Smallpox Diagnosis:
Initial diagnosis of smallpox is most likely based on a history and physical examination findings;
any person suspected of having the disease needs to be isolated, people caring for the patient
should use strict isolation-barrier techniques to protect themselves and others from exposure and
local, state and national health authorities should be informed immediately.
The doctor may take a throat swab to make the diagnosis of smallpox. A sample from a freshly
opened pustule may also be useful in diagnosis. For suspected cases of hemorrhagic smallpox,
the doctor may sample fluid from a spinal tap (lumbar puncture). Under certain conditions,
cytoplasmic inclusion bodies (also known as Guarnieri bodies) may be visible within the cells.
This is also evidence of smallpox infection.
Smallpox Treatment:
In the hospital's emergency department, a suspected smallpox victim is isolated. All emergency
medical services and hospital personnel exposed to someone with smallpox require quarantine
and vaccination if they have not been previously vaccinated.
Quarantine:
The infected person and anyone who has come into contact with the infected person for up to 17
days prior to illness (including the treating doctor and nursing staff) may be required to remain in
isolation until a definite diagnosis is made. If the suspected case is indeed smallpox, these
individuals will have to remain in isolation for at least 17 days to ensure that they are not also
infected with the virus.
Treatment:
Medical treatment for smallpox eases its symptoms. This includes replacing fluid lost from
fever and skin breakdown. Antibiotics may be needed for secondary skin infections. The infected
person is kept in isolation for 17 days or until the scabs fall off.
Smallpox Prevention:
Vaccination is the most effective means of preventing smallpox infection. Vaccination can even
be administered up to four or five days after a person is exposed to the virus. This practice may
not completely prevent disease, but probably it will result in a significantly less severe case of
the illness.
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Smallpox Vaccine:
There are no pills that can treat smallpox, but scientists are doing research to try to develop
medicine for the disease. If someone does become infected with the smallpox virus, getting the
vaccine within a few days of becoming infected can lessen the disease's symptoms
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The vaccinia (smallpox) vaccine and vaccinia immune globulin (VIG) are available only through
the CDC and state health agencies. The calf lymph vaccine is the only one still available although
a replacement vaccinia vaccine produced from cell cultures is under development.
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