Infection is a process in which bacteria,
viruses, fungi or other organisms enter
the body, attach to cells, and multiply. To
do this, they must evade or overcome the
body's natural defenses at each step.
Infections have the potential to cause
illness, but in many cases the infected
person does not get sick.
KEYWORDS
for searching the Internet and other
reference sources.
Antibiotics
Immunization
Infection
Inflammation.
HOW DOES INFECTION OCCUR?
Organisms that can cause illness are all
around us: in air, water, soil, and food,
as well as in the bodies of animals and
other people. Infection occurs when
some of them get past a series of natural
defenses. Those defenses include:
* Skin: The skin physically blocks germs,
but may let them in if it is cut or
scraped.
* Coughing deeply: This expels germs from
the lungs and breathing passages but
may be less effective for weak, sick, or
injured people.
* Bacteria: Called "resident flora," harmless
bacteria normally are present in some
parts of the body. They compete with
harmful germs and crowd them out. But
they can be weakened or killed by
medications, allowing harmful germs to
thrive and cause illness.
Inflammatory response: This is produced
by the body's immune system. Certain
kinds of white blood cells—including
macrophages and neutrophils—surround
and destroy or otherwise attack any kind
of germs, often causing fever, redness,
and swelling.
* Antibodies: These are proteins produced
by the immune system. Some are
targeted to attack specific microbes. This
response is also called humoral
immunity. Usually these antibodies are
produced after a person is infected by or
exposed to the microbe.
The immune system's responses may fail
if the germs are too numerous, or if they
are too virulent. "Virulent," from the
Latin for "poisonous," describes germs
that are particularly good at countering
the body's defenses. For instance, some
microbes can prevent antibodies from
forming against them. Another
important factor is the functioning of the
immune system. If it is damaged—
weakened, for instance, by age or illness
—infection is more likely. Babies tend to
get more infections because their
immune systems have not yet learned to
recognize and attack some microbes.
WHERE DOES INFECTION OCCUR?
Localized infections
Localized infections remain in one part
of the body. Examples include a cut on
the hand that gets infected with bacteria,
but does not cause problems anywhere
else. Localized infections can be very
serious if they are internal, such as in
the appendix (appendicitis ) or in the
heart (endocarditis ).
Systemic infections
Most serious infections, however, occur
when the microorganisms spread
throughout the body, usually in the
bloodstream. These are called systemic
infections, and they include flu, malaria,
AIDS, tuberculosis, plague, and most of
the infectious diseases whose names are
familiar.
How Do Infections Lead To Illness?
The major causes of infection are
viruses, bacteria, fungi, and parasites,
including protozoa (one-celled
organisms), worms, and insects such as
mites (which cause scabies) and lice.
Bacteria can release toxins, or poisons.
Viruses can take over cells and prevent
them from doing their normal work.
Bacteria and fungi—and larger infective
agents like worms or other parasites—
can multiply so rapidly that they
physically interfere with the functioning
of the lungs, heart, or other organs. The
immune response itself—which can
bring fever, pain, swelling, and fatigue—
often is the major cause of the sick
feelings an infected person gets.
Do Infections Always Cause Illness?
No, often they do not. Of people infected
with tuberculosis bacteria, for instance,
only about one in ten will ever get sick.
Some viruses and parasites, too, can
remain in the body a lifetime without
causing illness. In such cases, called
latent infection, people usually get sick
only if the immune system weakens.
How Do Infections Spread?
The organisms that cause infections may
spread through water, soil, food, or air;
through contact with an infected
person's blood, skin, or mucus ; through
sexual contact; or through insect bites.
Most germs spread by a couple of these
routes; no one microbe spreads in all
these ways. In addition, many disease-
causing microbes can spread from a
pregnant woman to her fetus. When this
happens, we say the baby is born with a
congenital infection.
What Are The Symptoms Of Infection?
The symptoms vary greatly depending on
the part of the body and type of
organism involved. The first sign of
bacterial infection is often
inflammation : fever, pain, swelling,
redness, and pus. By contrast, viral
infections less commonly cause
inflammation but may cause a variety of
other symptoms, from a runny nose or
sore throat to a rash or swollen lymph
nodes * .
What Is The Treatment For Infection?
The main treatment is usually
medication: antibiotics for bacterial
infections; antiviral drugs for some
viruses (for most there is no treatment);
antifungal medications for fungus
infections; and antihelmintic drugs for
worms. In some cases of localized
infection, as when an abscess or
collection of pus forms, surgery may be
necessary to drain the infected area.
How Are Infections Prevented?
Disinfecting wounds
When a wound occurs, infection may be
prevented by washing and covering the
wound, using antibacterial ointment or
spray, and getting medical attention if
the wound is serious.
Immunization
Many systemic infectious diseases can be
prevented by immunization. Among
them are chickenpox, cholera,
diphtheria, hepatitis A and hepatitis B,
influenza, Lyme disease, measles,
mumps, pertussis (whooping cough),
pneumococcal pneumonia, polio, rabies,
rubella (German measles), tetanus,
typhoid fever, and yellow fever.
Hygiene, sanitation, and public health
Many other systemic infections can be
prevented by having a clean public
water supply and a sanitary system for
disposing of human wastes; by washing
hands before handling food; by cooking
meats thoroughly; by abstaining from
sexual contact; and by controlling or
avoiding ticks and mosquitos.
* lymph nodes are round masses of tissue
that contain immune cells to filter out
harmful microorganisms. During
infections, lymph nodes may become
enlarged.
See also
Bacterial Infections
Fungal Infections
Immunodeficiency
Parasitic Diseases
Viral Infections
Worms
Post a Comment