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:: en Español
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SMALLPOX OVERVIEW
The disease Smallpox is a serious, contagious,
and sometimes fatal infectious disease. There is no specific treatment
for smallpox
disease, and the only prevention is vaccination. The name smallpox
is derived from the Latin word for “spotted” and refers
to the raised bumps that appear on the face and body of an infected
person.
There are two clinical forms of smallpox. Variola major is the
severe and most common form of smallpox, with a more extensive
rash and higher fever. There are four types of variola major
smallpox: ordinary [the most frequent type, accounting for
90% or more of
cases]; modified [mild and occurring in previously vaccinated
persons]; flat; and hemorrhagic [both rare and very severe].
Historically,
variola major has an overall fatality rate of about 30%; however,
flat and hemorrhagic smallpox usually are fatal. Variola minor
is a less common presentation of smallpox, and a much less severe
disease, with death rates historically of 1% or less.
Smallpox outbreaks have occurred from time to time for thousands
of years, but the disease is now eradicated after a successful
worldwide vaccination program. The last case of smallpox in
the United States was in 1949. The last naturally occurring
case
in the world was in Somalia in 1977. After the disease was
eliminated from the world, routine vaccination against smallpox
among the
general public was stopped because it was no longer necessary
for
prevention.
Where Smallpox Comes From
Smallpox is caused by the variola virus that emerged in human
populations thousands of years ago. Except for laboratory
stockpiles, the variola
virus has been eliminated. However, in the aftermath of the
events of September and October, 2001, there is heightened
concern that
the variola virus might be used as an agent of bioterrorism.
For this reason, the U.S. government is taking precautions
for dealing
with a smallpox outbreak.
Transmission
Generally, direct and fairly prolonged face-to-face contact
is required to spread smallpox from one person to another.
Smallpox
also can be spread through direct contact with infected
bodily fluids or contaminated objects such as bedding or clothing.
Rarely, smallpox has been spread by virus carried in the
air in enclosed
settings such as buildings, buses, and trains. Humans are
the only natural hosts of variola. Smallpox is not known
to be
transmitted by insects or animals.
A person with smallpox is sometimes contagious with onset
of fever [prodrome phase], but the person becomes most
contagious with the
onset of rash. At this stage the infected person is usually
very sick and not able to move around in the community.
The infected
person is contagious until the last smallpox scab falls
off.
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Smallpox Disease
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Incubation Period
[Duration: 7 to 17 days]
Not contagious |
Exposure to the virus is followed by an incubation period
during which people do not have any symptoms and may feel fine.
This incubation period averages about 12 to 14 days but can
range from 7 to 17 days. During this time, people are not contagious. |
Initial Symptoms [Prodrome]
[Duration: 2 to 4 days]
Sometimes
contagious* |
The first symptoms of smallpox include fever, malaise, head
and body aches, and sometimes vomiting. The fever is usually
high, in the range of 101 to 104 degrees Fahrenheit. At this
time, people are usually too sick to carry on their normal
activities. This is called the prodrome phase and may last
for 2 to 4 days. |
Early Rash
[Duration: about 4 days]
Most contagious |
A rash emerges first as small red spots on the tongue and
in the mouth.These spots develop into sores that break open
and spread large amounts of the virus into the mouth and throat.
At this time, the person becomes most contagious.
Around the
time the sores in the mouth break down, a rash appears
on the skin, starting on the face and spreading to the arms
and legs
and then to the hands and feet. Usually the rash spreads
to all parts of the body within 24 hours. As the rash appears,
the fever usually falls and the person may start to feel
better.
By
the third day of the rash, the rash becomes raised bumps.
By
the fourth day, the bumps fill with a thick, opaque fluid
and often have a depression in the center that looks like
a bellybutton.
[This is a major distinguishing characteristic of smallpox.]
Fever
often will rise again at this time and remain high until
scabs form over the bumps. |
Pustular Rash
[Duration: about 5 days]
Contagious |
The bumps become pustules—sharply raised, usually round
and firm to the touch as if there’s a small round object
under the skin. People often say the bumps feel like BB pellets
embedded in the skin. |
Pustules and Scabs
[Duration: about 5 days]
Contagious |
The pustules begin to form a crust and then scab. By the
end of the second week after the rash appears, most of the
sores have scabbed over. |
Resolving Scabs
[Duration: about 6 days]
Contagious |
The scabs begin to fall off, leaving marks on the skin that
eventually become pitted scars. Most scabs will have fallen
off three weeks after the rash appears.The person is contagious
to others until all of the scabs have fallen off. |
Scabs resolved
Not contagious |
Scabs have fallen off. Person is no longer contagious. |
* Smallpox may be contagious during the prodrome phase, but is
most infectious during the first 7 to 10 days following rash onset.
:: en Español
::
The contents of this page, as well as other information on bioterrorism,
are provided by:
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Loretta V. Davis ,
MSA,
Health Officer
Christine Hensley , Emergency Preparedness Coordinator
Joyce Brown-Williams
Public Information Manager
Emergency Preparedness
33030 Van Born Road
Wayne, MI 48184
Ph: 734-727-7827
In case of a public health emergency during non-business hours, weekends and on holidays, call
Ph: 734-727-7284
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