Plague
Plague
Also called: Bubonic plague, Pneumonic plague
Plague is an infection caused
by the bacterium Yersinia pestis. The bacteria are found mainly in rats and in
the fleas that feed on them. People and other animals can get plague from rat
or flea bites. In the past, plague destroyed entire civilizations. Today plague
is uncommon, due to better living conditions and antibiotics.
There are three forms of
plague:
·
Bubonic plague causes the
tonsils, adenoids, spleen, and thymus to become inflamed. Symptoms include
fever, aches, chills, and tender lymph glands.
·
In septicemic plague, bacteria
multiply in the blood. It causes fever, chills, shock, and bleeding under the
skin or other organs.
·
Pneumonic plague is the most
serious form. Bacteria enter the lungs and cause pneumonia. People with the
infection can spread this form to others. This type could be a bioterror agent.
Lab tests can diagnose plague.
Treatment is a strong antibiotic. There is no vaccine.
NIH: National Institute of Allergy and Infectious Diseases
Plague
Overview
Plague is an infectious disease caused by
bacteria called Yersinia pestis.
These bacteria are found mainly in rodents, particularly rats, and in the fleas
that feed on them. Other animals and humans usually contract the bacteria from
rodent or flea bites.
Historically,
plague destroyed entire civilizations. In the 1300s, the "Black Death,"
as it was called, killed approximately one-third (20 to 30 million) of Europe's
population. In the mid-1800s, it killed 12 million people in China. Today,
thanks to better living conditions, antibiotics, and improved sanitation,
current World Health Organization statistics show there were only 2,118 cases
in 2003 worldwide.
Approximately
10 to 20 people in the United States develop plague each year from flea or
rodent bites—primarily from infected prairie dogs—in rural areas of the
southwestern United States. About 1 in 7 of those infected die from the
disease. There has not been a case of person-to-person infection in the United
States since 1924.
Worldwide,
there have been small plague outbreaks in Asia, Africa, and South America.
Forms of Plague
Y. pestis can affect people in three different
ways: bubonic,
septicemic, or pneumonic plague.
Bubonic plague
In
bubonic plague, the most common form, bacteria infect the lymph system and
become inflamed. (The lymph or lymphatic system is a major component of your
body's immune system. The organs within the lymphatic system are the tonsils,
adenoids, spleen, and thymus.)
How
do you get it?
Usually,
you get bubonic plague from the bite of an infected flea or rodent. In rare
cases, Y. pestis bacteria, from a piece of contaminated
clothing or other material used by a person with plague, enter the body through
an opening in the skin.
What
are the symptoms?
Bubonic
plague affects the lymph nodes (another part of the lymph system). Within 3 to
7 days of exposure to plague bacteria, you will develop flu-like symptoms
such as fever, headache, chills,
weakness, and swollen, tender lymph glands (called buboes—hence the
name bubonic).
Is
it contagious?
Bubonic
plague is rarely spread from person to person.
Septicemic plague
This
form of plague occurs when the bacteria multiply in the blood.
How
do you get it?
You
usually get septicemic plague the same way as bubonic plague—through a flea or
rodent bite. You can also get septicemic plague if you had untreated bubonic or
pneumonic plague.
What
are the symptoms?
Symptoms
include fever, chills, weakness, abdominal pain, shock, and
bleeding underneath the skin or other organs. Buboes, however, do not develop.
Is
it contagious?
Septicemic
plague is rarely spread from person to person.
Pneumonic plague
This
is the most serious form of plague and occurs when Y. pestis bacteria
infect the lungs and cause pneumonia.
How
do you get it?
You
get primary pneumonic plague when you inhale plague bacteria from an infected
person or animal. You usually have to be in direct or close contact with the ill
person or animal. You get secondary pneumonic plague if you have untreated
bubonic or septicemic plague that spreads to your lungs.
What
are the symptoms?
Symptoms
usually develop within 1 to 3 days after you are exposed to airborne droplets
of plague bacteria. Pneumonia begins quickly, with shortness of breath, chest
pain, cough, and sometimes bloody or watery sputum. Other symptoms include
fever, headache, and weakness.
Is
it contagious?
Pneumonic
plague is contagious. If someone has pneumonic plague and coughs, droplets
containing Y. pestis bacteria from their lungs are released
into the air. An uninfected person can then develop pneumonic plague by
breathing in those droplets.
Transmission
Y. pestis is found in animals throughout the
world, most commonly in rats but occasionally in other wild animals, such as
prairie dogs. Most cases of human plague are caused by bites of infected
animals or the infected fleas that feed on them. In almost all cases, only the
pneumonic form of plague (see Forms of Plague) can be passed from person to
person.
Diagnosis
A
health care provider can diagnose plague by doing laboratory tests on blood or
sputum, or on fluid from a lymph node.
Treatment
When
plague is suspected and diagnosed early, a health care provider can prescribe
specific antibiotics (generally streptomycin or gentamycin). Certain other
antibiotics are also effective.
Left
untreated, bubonic plague bacteria can quickly multiply in the bloodstream,
causing septicemic plague, or even progress to the lungs, causing pneumonic
plague.
Prevention
Antibiotics
Health
experts recommend antibiotics if you have been exposed to wild rodent fleas
during a plague outbreak in animals, or to a possible plague-infected animal.
Because there are so few cases of plague in the United States, experts do not
recommend taking antibiotics unless it's certain a person has been exposed to
plague-infected fleas or animals.
Vaccine
Currently,
there is no commercially available vaccine against plague in the United States.
Research
The
National Institute of Allergy and Infectious Diseases (NIAID) conducts and
supports research on the diagnosis, prevention, and treatment of infections
caused by microbes, including those that have the potential for use as
biological weapons. The research program to address biodefense includes both
short- and long-term studies targeted at designing, developing, evaluating, and
approving specific tools (diagnostics, drugs, and vaccines) needed to defend
against possible bioterrorist-caused
disease outbreaks.
For
instance, NIAID-supported investigators sequenced the genome of the strain
of Y. pestis that was associated with the second pandemic of
plague, including the Black Death. This will provide a valuable research resource
to scientists for identifying new targets for vaccines, drugs, and diagnostics
for this deadly pathogen.
NIAID-funded
scientists have developed a rapid diagnostic test for pneumonic plague that can
be used in most hospitals. This will allow health care providers to quickly
identify and isolate the pneumonic plague patient from other patients and
enable health care providers to use appropriate precautions to protect
themselves.
Many
other plague research projects at NIAID are focusing on early-stage vaccine
development, therapeutics, and diagnostics. Y. pestis bacterium
is a high priority with funded efforts ranging from basic science research to
final product development.
Current
research projects include:
- Identifying
genes in Y. pestis that infect the digestive tract of
fleas and researching how the bacteria are transferred to humans
- Studying
the disease-causing proteins and genes of Y. pestis that
allow the bacteria to grow in humans and learning how they function in
human lungs
NIAID
is also working with the U.S. Department of Defense, the Centers for Disease
Control and Prevention, and the U.S. Department of Energy to:
- Develop
a vaccine that protects against inhalationally acquired pneumonic plague
- Develop
promising antibiotics and intervention strategies to treat and prevent
plague infection
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